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Journal of the 

Society of Motion Picture Engineers 

VOLUME 53 JULY 1949 NUMBER 1 

PAGE 

Processing Control Procedures for Ansco Color Film 

J. E. BATES AND I. V. RUNYAN 3 

Analysis of Developers and Bleach for Ansco Color Film 

A. H. BRUNNER, JR., P. B. MEANS, JR., AND R. H. ZAPPERT 25 

Note on an Improved Filter Holder for Color Printing 

THEODORE J. BRAUN 36 

Metallic-Salt Track on Ansco 16-Mm Color Film 

J. L. FORREST 40 

Laboratory for Development Work on Color Motion Pictures ... 

H. C. HARSH AND K. SCHADLICH 50 

1000-Foot Bipack Magazine and Adapter 

WILTON R. HOLM AND JAMES W. KAYLOR 58 
Cathode-Ray-Tube Applications in Photography and Optics.. . 

CARL BERKLEY AND RUDOLF FELDT 64 

Objective Lenses of //I Aperture and Greater 

EDWARD K. KAPRELIAN 86 

66th Semiannual Convention 100 

Edward Auger ... 102 

Book Reviews: 

" Comparative List of Color Terms/' Published by the Inter- 
Society Color Council 

Reviewed by John L. Forrest 103 

"Physical Aspects of Colour," by P. J. Bouma 

Reviewed by Ralph M. Evans. 103 

"Better Color Movies," by Fred Bond 

Reviewed by Lloyd Thompson 104 

New Products 106 

ARTHUR C. DOWNES HELEN M. STOTE NORWOOD L. SIMMONS 

Chairman Editor Chairman 

Board of Editors Papers Committee 

Subscription to nonmembers, $10.00 per annum; to members, $6.25 per annum, included in 
their annual membership dues; single copies, $1.25. Order from the Society's General Office. 
A discount of ten per cent is allowed to accredited agencies on orders for subscriptions and 
single copies. Published monthly at Easton, Pa., by the Society of Motion Picture Encineers, 
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342 Madison Ave., New York 17, N. Y. Entered as second-class matter January 15, 1930, 
at the Post Office at Easton, Pa., under the Act of March 3, 1879. 

Copyright, 1949, by the Society of Motion Picture Engineers, Inc. Permission to republish 
material from the JOURNAL must be obtained in writing from the General Office of the Society. 
Copyright under International Copyright Convention and Pan-American Convention. The 
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Society of 

Motion Picture Engineers 

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EXECUTIVE 
VICE-PRESIDENT 
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OFFICERS 

1949-1950 

PAST-PRESIDENT 
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EDITORIAL 
VICE-PRESIDENT 
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1948-1949 



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VICE-PRESIDENT 
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SECRETARY 
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CONVENTION 
VICE-PRESIDENT 
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1949 

FINANCIAL 
VICE-PRESIDENT 
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1948-1949 

Alan W. Cook 
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Governors 
1949 

James Frank, Jr. 
426 Luckie St., N. W. 
Atlanta, Ga. 

William B. Lodge 
485 Madison Ave. 
New York 22, N. Y. 

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4431 W. Lake St. 
Chicago 24, 111. 



1949-1950 

Herbert Barnett 
Manville Lane 
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Fred T. Bowditch 
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Norwood L. Simmons 
6706 Santa Monica Blvd. 
Hollywood 38, Calif . 



Processing Control Procedures 
for Ansco Color Film* 

BY J. E. BATES AND I. V. RUNYAN 

ANSCO, BlNGHAMTON, NEW YORK 

Summary Reproducible processing of Ansco color film requires con- 
tinuous control of the solution compositions. Early experience showed that 
frequent change of processing solutions was necessary to maintain consist- 
ency. New replenisher formulas are described which together with sensito- 
metric controls and occasional chemical analysis have proved successful for 
maintaining the processing solutions in a satisfactory condition indefinitely. 
Color-balance differences resulting from varied types of agitation, depending 
on the processing equipment, may be adjusted by changing the chemical 
constitution of the first developer. 

THE CONTINUOUS processing of Ansco color film requires control of 
speed, gradation, fog, D-max., and other variables common to the 
processing of black-and-white films, but with the complicating factor 
that these variables must be kept constant in each of three super- 
imposed emulsion layers. 

When this color film was first introduced, frequent changes of proc- 
essing solutions were advised to prevent the deteriorating effects of 
aging and exhaustion. With experience, methods of processing con- 
trol gradually have evolved using continuous replenishing procedures 
controlled by sensitometric and analytical tests. This paper pre- 
sents an outline of the essential control steps necessary at each operat- 
ing stage of a processing laboratory. Through the use of these 
practices an experienced control man can maintain a set of processing 
solutions indefinitely. Tests are outlined not only for actual machine 
operations but also to check raw chemicals and individual mixes of 
solutions. Although essentially designed for motion picture labora- 
tories, the basic methods are also applicable to roll- and sheet-film 
processing units, and with different developer replenishers, to the 
processing of Printon. 

I. BASIC CONTROL METHODS 

Three general control methods, photographic, analytical and pH, 
are recommended for the various testing operations. The necessary 

* Presented May 18, 1948, at the SMPE Convention in Santa Monica. 

JULY, 1949 JOURNAL OF THE SMPE VOLUME 53 3 



BATES AND RUNYAN 



July 



tests are outlined briefly in Fig. 1. For simple solutions such as short 
stop and hardener, simple pH tests suffice. For developer solutions 
and actual machine controls, both photographic and analytical tests 
are necessary. A chemical standard is used as the basis for all tests. 
A supply of high-purity chemicals should be maintained as the proc- 
essing standards and type solutions should be prepared from these 
chemicals with accurate mixing. 

A. ^H Tests 

pH is controlled with Coleman or Beckman Laboratory Model pH 
instruments using glass-calomel electrode systems. Other instru- 




Fig. 1 

ments of equal sensitivity would suffice. All pH readings including 
those of developers given in the paper are based on the use of a normal 
glass electrode. It is recognized that the use of an electrode intro- 
duces sodium ion errors due to the high salt concentration of the solu- 
tion, but in practice, since the salt concentration remains constant, 
consistent and useful readings are obtained and no attempt is made to 
correct the data. If a special electrode designed for high salt concen- 
trations at a high pH (10 to 11) is used, the developer pH readings 
will range about 0.10 higher than indicated in this paper. It is to be 
emphasized that except for short stop and hardener solutions which 
are fully controlled by pH, the pll values are used merely as a guide. 



1949 COLOR PROCESSING CONTROL 5 

Solutions can be rejected and trouble located if pH measurements fall 
outside normal limits, but proper pH does not insure satisfactory 
performance. 

B. Photographic Tests. 

These can be divided into two parts: (1) photographic solution 
control tests, and (2) photographic tests made on the machine during 
operation. 

1 . Photographic Solution Control Tests 

Tests so termed are used for testing raw materials, solution mixes, 
and in locating possible sources of trouble with machine solutions. 
The photographic test consists simply in processing duplicate sensito- 
metric strips of color film through the standard cycle of color-film proc- 
essing except that the strips are separated at the solution to be 
tested and one strip run through the sample solution and one through 
the type solution. These sensitometric strips should be exposed on 
the same type of color emulsion the machine will process. A supply 
of film of a single emulsion number sufficient for several months' con- 
trol operation should be set aside to avoid too frequent typing in of 
emulsions. Either time or intensity-scale sensitometry may be used, 
although intensity-scale instruments are recommended because they 
give a more accurate indication of a film's practical performance. 
The instrument, however, must be capable of highly reproducible re- 
sults and should be adjusted to produce a color balance close to 
neutral. Both visual and densitometer measurements are more 
accurate when made with neutrally exposed film. Latent-image 
changes in exposed strips are normally of small magnitude. How- 
ever, it is recommended for optimum consistency that no exposures 
more than two months old be used for control work. 

It is essential that solution testing be done under carefully con- 
trolled conditions of agitation, time, and temperature so that the 
system itself has reproducibility greater than the solution tolerance 
to be tested. In practice it is possible to construct apparatus that 
will give results deviating by not more than 1 /s stop speed or Vi 6 stop 
color balance when identical solutions are used for type and sample. 
This degree of reproducibility requires mechanical agitation, water 
baths for solution temperature control, and methods of quickly chang- 
ing film from solution to solution. In the Ansco laboratory, an ap- 
paratus has been constructed employing a series of stainless-steel 



6 



BATES AND RUNYAN 



July 



tubes each holding \. l / z liters of solution (Figs. 2 and 3). Special 
racks each holding two 35-mm strips in a film slide-type holder fit 
into the tubes. A rubber-edged vane, with a vertical movement 
operated by a series of pulleys over the tubes, is built into each rack. 
The whole unit is set into a water bath with temperature control. It is 
not necessary to employ exactly this design of apparatus, but mechani- 
cal agitation is strongly recommended. 

Photographic solution control tests are interpreted by reading the 
color densities of the type and sample sensitometric strips on an 




Fig. 2 

Ansco color densitometer 1 and comparing the plotted results for 
speed, density, and color-balance differences. Acceptable tolerances 
in processing solutions necessarily are high but specific acceptable 
limits must depend somewhat on circumstances. In general, solu- 
tions can be accepted that do not give speed differences greater than 
I /A stop or color-balance differences greater than 1 / 8 stop from type. 
Should an occasion arise where both the first developer and color 
developer or their respective replenishers show 1 / 8 stop color-balance 
difference, both in the same direction, the combination obviously 
would produce an intolerable result on the machine. 

Normal machine-processing times are recommended for the solution 



1949 



COLOR PROCESSING CONTROL 



control test machine except replenisher solutions are tested with two 
thirds the developing time of their basic solutions. It is desirable, al- 
though not absolutely necessary, that the solution control test machine 
and the processing machine turn out closely matched results. Often 
differences in agitation will make this difficult. The procedure for 
chemically adjusting color balance described in the section on machine 
adjustments would not be applicable in this case because it is neces- 
sary that the solution control machine operate to test the exact 
machine formulas. 




Fig. 3 

2. Photographic Tests of Machine Operation 

The basic purpose behind all preliminary testing is, of course, to 
control the actual developing machine. To this end the greatest 
reliance is placed on photographic controls because these indicate 
directly the results the machine is producing. Test strips are run 
through at 15- to 30-minute intervals. As the strips come off the 
machine, they are quickly compared visually with the preceding- 
strips and the color densities of three representative toe, middletone, 
and shoulder steps read and plotted as shown in Fig. 4. The control 
chart that gradually accumulates as a result of plotting these 



8 



BATES AND RUNYAN 



July 



continuous strips is of great value in controlling the machine. By 
connecting the points as the graph is constructed, a running record is 
obtained of the speed and color-balance fluctuations. Speed increases 
in reversible film are denoted by a drop in all layer densities, a speed 
decrease by a rise in all densities, while color-balance shifts are de- 
noted by unequal changes in the various layer densities. 

As can be seen from Fig. 4, minor fluctuations in over-all speed and 



GRAPHICAL RECORD OF 
MACHINE OPERATION 



-MAGENTA 
CYAN 
YELLOW 



6AM 



12PM 4PM 8PM 12AM 

CONSECUTIVE CONTROL STRIPS - APPROX. 1/2 HR. INTERVALS 



3 30AM 



Fig. 4 

very slight deviations in color balance occur between successive 
developments. These fluctuations are normal in the best regulated 
machines made to date and are caused by a variety of effects all minor 
in character but which add up to measurable differences. 

The variables which cannot be absolutely controlled include slight 
differences in film emulsions, film exposures, chemicals, solution mixes, 
developing times and temperatures, circulation rates, drying condi- 
tions, and even final densitometry. These additive deviations may 
amount to as much as plus or minus ! /4 stop speed variation as well as 
color-balance shifts of plus or minus l /s stop. It is the controlman's 
responsibility to distinguish between a fluctuation that is within the 



1949 



COLOR PROCESSING CONTROL 



9 



optimum operating capability of his apparatus and a deviation that 
represents improper control. For this reason, graphical methods are 
employed. By following such a graph, it is possible to control the 
machine output within narrow limits. Fig. 5 illustrates another series 
of developments; it can be seen that for developments A through B 
fluctuations ranged upward and downward in a fairly regular pattern. 
This was normal machine operation. Beginning with B, although the 
fluctuations were still up and down, the majority was running higher 




GRAPHICAL RECORD OF 
MACHINE OPERATION 



MAGENTA I 

CYAN 

YELLOW 




3 30 AM 



6AM 12PM 4PM 8P> 

CONSECUTIVE CONTROL STRIPS - APPROX 1/2 HR. INTERVALS 



Fig. 5 



than normal in density. This to the controlman indicated a definite 
trend toward lower speed that would require corrective measures. 
Since this rise was accompanied by a slight gain in the magenta and 
yellow density over the cyan layer in the middletone region (density 
1.2) and also in the shoulder densities, he increased the replenishment 
rate of the first developer by 10 per cent. As can be seen by C" to D 
(film C to C' had passed through the first developer before the correc- 
tion could be applied), this change of replenishment rate achieved the 
desired result as the speed increased and the color balance became more 
neutral. 



10 BATES AND RUNYAN July 

In case of questionable deviations in the graph, complete sensito- 
metric curves should be plotted for the strips involved. For general 
purposes, the three-step plot will suffice. 

Many machine operators will prefer to run a pictorial type in addi- 
tion to the sensitometric type since this gives them a clearer picture of 
the actual effect of machine differences on picture quality. The inter- 
pretation of pictorial strips should, of course, be given secondary 
emphasis as compared to the more accurate, numerical interpretation 
of the sensitometric control strips. 

When deviations occur in the machine photographic tests, it is 
advisable to run a chemical analysis immediately to fix the cause of the 
deviation. Photographic side tests also may be made by using the 
solution control machine to compare a solution withdrawn from a 
machine tank with a type solution. Provided proper prechecking of 
solutions is made at the tune of mixing, no serious deviations ever 
should occur. Such differences as do occur will normally arise from 
an excessive amount of high or low key film exposures, or from exces- 
sive aeration of solution due to leaky circulation pumps or from the 
aging of unused solutions. 

C. Analytical Controls 

The analysis procedure for the developer and bleach solutions are 
outlined in the paper by Brunner, Means, and Zappert. 2 For routine 
machine operation, complete developer analysis should be run ap- 
proximately every 48 hours. Bromide analysis of developers should 
be run every 4 to 8 hours as changes in bromide concentration are an 
accurate indication of improper replenishment rate. Bleach tit rations 
should be run at 8-hour intervals. The condition of the bleach can 
be judged roughly by visually noting the time required for the bleach 
to etch out the silver antihalo layer. Bleach performance is generally 
satisfactory if this takes place in 1 / 3 the total bleaching time. It 
should never exceed l / 2 the total bleaching time. 

The fixer tank should be analyzed for silver content at intervals of 
8 hours of machine operation. Fixer performance is satisfactory if 
tune of clearing does not exceed l / z total time of fixing. 

II. MACHINE CONTROL AND REPLENISHMENT DATA 

Successful replenishment can be carried out on any type of equip- 
ment having fully controlled and reproducible temperature and 
agitation conditions. Within the Ansco plant, the system has been 



1949 COLOR PROCESSING CONTROL 11 

adopted to machines used for 16-mm film processing as described by 
Forrest, 3 for 35-mm film processing as described by Harsh and 
Schadlich, 4 and for rack-type sheet-film processing machines varying 
from a large Pako machine to small vane-agitated 3V2-gallon tanks. 
The value of replenishment is questionable for hand-agitation sys- 
tems. The greatest control normally is obtained with the larger size 
machines that are in constant rather than intermittent use. It is 
desirable to maintain continuous filtration systems in both color and 
first-developer tanks as the build-up of gelatin particles, specks of 
oxidized developer, and other foreign material hasten the chemical 
breakdown of solutions. Proper filtration will keep both first de- 
veloper and color developer clear and light in color after months of 
operation. 

A. Modification of Processing Solutions to Change Color Balance 

The widely varying agitation conditions existing in the different 
types of processing equipment introduce a complicating factor be- 
cause variations in agitation can produce different color balances. 
Partial compensation for these balance differences can be obtained by 
increasing or decreasing developing tunes. However, in order to 
achieve the closest possible matches in speed, gradation, and color 
balance, it is sometimes necessary to make slight chemical changes in 
the processing solutions themselves. 

The most convenient tools for modifying color-balance differences 
resulting from different agitation conditions are variations of the 
thiocyanate and iodide concentrations in the first developer solution. 
Chemical analysis of No. 502 first developer has shown that iodide 
accumulates during film development, and, depending somewhat on 
the type of film processed, exposure level and volume of replenisher 
added, normally reaches an equilibrium of from 3 to 6 milligrams per 
liter of developer. Iodide-analysis methods and a discussion of 
iodide equilibrium for black-and-white film developers were given by 
Evans, Hanson, and Glasoe. 5 6 

Practical tests with color film show that even a small concentration 
of iodide exerts an appreciable restraining effect on the yellow and 
magenta layers giving an effective speed loss in these layers and a 
shift in the- over-all color balance toward the brown. It can be shown 
that accumulation of iodide is responsible for a large part of the color- 
balance shifts that occur when a first developer is used. If small 



12 BATES AND RUNYAN July 

amounts of potassium iodide are added initially to the fresh developer, 
the color-balance changes are reduced. We have adopted the prac- 
tice of adding small quantities of potassium iodide to fresh No. 502 
first developer. No iodide is added to the replenisher solution. 

Under processing conditions where only moderate agitation is 
encountered (as in Pako processing) bluish-cyan color balances are 
often encountered because the first developer is most active on the top 
layers of the film and does not easily penetrate to the bottom layer. 
Increased first development tunes under such conditions do not change 
the relative rates of development in the layers. However, the main- 
tenance of a higher than normal iodide concentration will restrain first 
development in the top layers more than hi the cyan layer and by use 
of slightly longer than normal developing tunes, a normal color bal- 
ance can be achieved. In this case, it is necessary to maintain this 
high iodide concentration by adding a small amount to the replenisher 
solution. 

The above color-balance shifts are essential for the processing of 
Types 234, 634, 235, and 635 sheet, roll, and 35-mm cartridge films 
since these materials must be balanced so they can be processed suc- 
cessfully both by amateurs with hand-processing outfits and by factory 
finishing. Obviously it is not necessary to achieve a so-called normal 
balance for a machine used to process a printing-type film whose 
balance is normally modified by printing filters, but it is of course 
essential that whatever balance is obtained be maintained 
consistently. 

B. Replenishment Procedure 
1. General 

The following developer replenishes were worked out using the 
solution analysis technique described by Brunner, Means, and 
Zappert. 2 Although the exact replenishment rates may require ad- 
justment from time to time, use of the replenishers will maintain the 
solution ingredients very close to their initial concentrations. 

Greater than 10 per cent variation in replenishment rates rarely are 
necessary. Trends that are not corrected by such changes eventually 
are traced to a mechanical or physical fault. Such difficulties should 
be solved by chemical analysis of the solutions in doubt. Through 
the knowledge of the film response to different chemical variations, 
skilled controlmen have maintained consistent color balances and 



1949 COLOR PROCESSING CONTROL 13 

speed over months of operation. The exact effects produced by 
photographic variations differ somewhat among different emulsions 
depending on the exact color balance of the emulsion. In general, 
variations of color developer affect the heavier densities to a greater 
degree than the lower densities whereas variations in first developer 
cause deviations in the over-all speed and balance of the film. 

Relatively large quantities of replenishers are utilized in most 
cases. In the first developer, the rate is high to avoid build-up of 
bromide in the developer. In the color developer, replenishment rate 
is high because the replenisher solution is nearly as concentrated as 
possible. Bromide accumulates so slowly in the color developer it is 
necessary to add it in the replenisher solution to maintain the origi- 
nal amount. The short stop and hardener solutions are replenished 
at these high rates to prevent excessive accumulation of contaminants. 
No continuous replenishment is used with the bleach and fixing baths. 
The bleach is shifted to a separate tank, rejuvenated with bromine and 
after adding additional salts to make up for those lost by dilution, is 
returned to the machine tank. The fixer is used to exhaustion, then 
dumped into a large crock for sulfide recovery of silver. 

2. Detailed Replenishment Procedure 

The replenishment rates given in this paper are based on the rates 
used for the Ansco 16-mm and 35-mm developing machines. Other 
machines may perform best with slightly modified conditions or for- 
mulas. In fact, replenishment rates normally vary slightly during 
routine operation of any single machine. However, the formulas and 
rates of replenishment listed provide a close approximation of the 
requirements of any machine and are to be recommended as a starting 
point. 

The developer replenishers were formulated using solution-analysis 
techniques and when used in combination with photographic and 
analysis tests have maintained developers over periods of months in 
the Ansco laboratories. 

It is recommended that 3.5 to 5.0 milligrams per liter of potassium 
iodide be added to fresh tanks of No. 502 first developer. Analysis 
data indicate that the normal iodide-equilibrium ranges around these 
figures, subject somewhat to the exposure level of the film processed. 

Changes in first developer activity are evidenced by over-all speed 
changes of the complete film. The exact color-balance differences 



14 BATES AND RUNYAN July 



TABLE I 
FIRST DEVELOPER REPLENISHMENT 





No. 502 First 
Developer 


No. 502 R-3 First 
Developer Replenisher 


Calgon 


Igram 


1 . gram 


Metol 


3 


3.2 


Sodium Sulfite 


50 


50.0 


Hydroquinone 


6 


7.5 


Sodium Carbonate 


40 


40.0 


Potassium Bromide 


2 


. 


Sodium Thiocyanate 


2 


2.4 


Sodium Hydroxide 




1.1 


Water to make 


1 liter 


1.0 liter 


Basic replenishment rate 23 


cc./ft. 35-mm film 



obtained by increased or decreased amounts of first development vary 
slightly from film to film but generally increases of first development 
show up as reduced magenta density in the balance. 



TABLE II 
SHORT STOP REPLENISHMENT 





No. 859 Short 
Stop 


No. 858 Short Stop 
(Replenisher for No. 859) 


Glacial Acetic Acid 
Sodium Acetate 
Water to make 


5cc. 
30 grams 
1 liter 


10 cc. 

20 grams 
1 liter 



pH fresh 5.20-5.30 pH fresh 4.70-4.80 
Basic replenishment rate 24 cc./ft. 35-mm film 



This solution is replenished at a rate necessary to maintain a pH of 
5.0 to 5.5. The volume of replenisher is great enough to provide 
sufficient solution change to prevent accumulation of excessive de- 
veloper solution. If the short stop pH is maintained at a higher pH 
than 5.5, increased hardening will result from the No. 901 hardener, 
but reduced short stopping action and scumming will be obtained. 
A pH lower than 5.0 produces less hardening by the No. 901 hardener 
and a pH lower than 4.5 may give difficulty with film blistering. 



1949 COLOR PROCESSING CONTROL 15 

TABLE III 

HARDENER REPLENISHMENT 
(These statements apply to the solution used after either first or color developer) 

No. 901 Hardener No. 901 Replenisher 

Potassium Chrome Alum 30 grams 30 grams 

Water to make 1 liter 1 liter 

Basic replenishment rate 30 cc./ft. 35-mm film 



This solution is replenished with the same solution as the original 
at a rate necessary to keep the tank pH approximately 3.5 to 4.0. If 
the pH rises above 4.5 (although the hardening effect will increase up 
to a pH of about 5.0) chrome alum sludge and scum may also result. 
If the pH. falls below 3.5, reduced hardening is obtained. Since a 
solution of chrome alum will hydrolyze on standing, the subsequent 
release of acid causes a natural drop of pH. The carry-over of a small 
quantity of alkali is not undesirable because it aids in maintaining the 
optimum pH. 

TABLE IV 
COLOR DEVELOPER REPLENISHMENT 



A-605 Color 
Developer 


A-605 R-2 Color 
Developer 
Replenisher 


Calgon 1 . gram 
Sodium Bisulfite 2.0 


1 . gram 
2.3 


S-3 4.0 


5.6 


Sodium Carbonate 67 . 5 


80.0 


Potassium Bromide 1 . 


0.6 


Water to make 1 liter 


lliter 


Basic replenishment rate 23 cc./ft. 


35-mm film 



Use of this replenisher, like the first developer replenisher, is de- 
signed to maintain the original concentration of developer ingredi- 
ents. Regular bromide analysis will assist in maintaining the proper 
replenishment rate. No iodide is added to this bath. Analysis indi- 
cates some iodide is accumulated during use but the formula is rela- 
tively insensitive to this restrainer in the quantities involved. 



16 BATES AND RUNYAN July 

TABLE V 
BLEACH REPLENISHMENT 

No. 713 Bleach 

Mono Sodium Dibasic Potassium Ferricyanide 100 grams 
Potassium Bromide 15 

Dibasic Sodium Phosphate 40 

Sodium Bisulfate 25 

Water to make 1 liter 



It is recommended that No. 713 bleach be rejuvenated intermit- 
tently with bromine additions. 

During normal bleaching operations, the bleach exhausts caused by 
depletion of ferricyanide and bromide ions as well as from dilution of 
the bleach solution by water carried into the tank by the wet film. 
The accumulation of ferrocyanide ions slows the rate of bleaching to a 
much greater extent than would be predicted from the depletion of 
ferricyanide. In practice, a concentration of potassium ferrocyanide 
greater than 5 grams per liter should be avoided. These concentra- 
tions can be detected using either the potentiometer method described 
by Brunner, Means, and Zappert 2 or, if desired, the colorimetric 
method described by Varden and Seary. 7 

The ferrocyanide can then be reoxidized to ferricyanide by the 
direct addition of liquid bromine to the solution. This reaction pro- 
duces bromide ions equivalent to the number of reoxidized ferricyanide 
ions and thus effectively regenerates the bleach bath. The chemical 
reactions of bleach exhaustion and rejuvenation are shown in 
Table VI. 

TABLE VI 

BLEACH EXHAUSTION 



4Ag + 4K 3 Fe(CN) 6 -- > Ag 4 Fe(CN) 6 
Ag 4 Fe(CN) 6 + 4KBr - > K<Fe(CN) 6 + 4AgBr 



BLEACH REJUVENATION 



4K4Fe(CN) + 4Br - > 4K3Fe(CN) e + 4KBr 



It is recommended that a bleach bath be rejuvenated at intervals 
corresponding to 25 feet of 35 millimeters per liter of tank solution. 



1949 COLOR PROCESSING CONTROL 17 

This is conveniently done by providing two hard-rubber or ceramic 
mixing tanks for the bleach with pumps so that the solution may be 
pumped from the machine tank to either mixing tank for the rejuvena- 
tion treatment while machine operation is continued using the other 
tank of bleach solution. 

A bleach exhaustion of 25 feet per liter normally corresponds to a 
potassium-ferrocyanide concentration of 4.5 to 5.0 grams per liter. 
With most technical grades of bromine, roughly 1.05 grams or 0.33 
cubic centimeter per liter would be required to rejuvenate the bleach 
completely. In practice, however, in order to avoid the danger of 
adding an excess of bromine which would give excessive fuming and 
would be dangerously active both on the color film and on the tanks, 
spool banks, and so forth, it is desirable to retain a small amount of 
ferrocyanide in the bleach, normally 1.0 gram per liter or equivalent 
to the exhaustion produced by 5 feet of film per liter. 

The addition of bromine should be made in a well-ventilated room 
or with a hood over the tank. Protective clothing and goggles should 
be worn as contact with the bromine will cause bad burns. The 
addition should be made slowly with vigorous stirring continued for a 
minimum of 30 minutes after the bromine addition is complete. The 
bromine will be assimilated more rapidly and with less fuming if it is 
first dissolved in 5 to 10 tunes its own volume of cold methanol and 
the mixture then added to the bleach mixing tank. 

A second potentiometer titration should be made after the bromine 
addition to check the accuracy of the replenishment. 

8. Replenishment of Diluted Bleach 

The dilution of the bleach by the wet film can be corrected by mak- 
ing additions of the original chemicals in the same proportion as they 
were originally compounded. The degree of dilution can be detected 
by specific-gravity measurements using a hydrometer. No chemical 
additions are necessary unless the dilution exceeds 10 per cent. The 
specific gravity of fresh bleach No. 713 is approximately 1.110 at 20 
degrees centigrade. Upon dilution, the specific gravity is reduced. 
An estimate of the degree can be made from the following calculation : 

Specific Gravity of Fresh Bleach Minus 

Specific Gravity of Diluted Bleach X 100 

-rf j-= , p. . , . ::. = Per Cent Loss of Dry . 

^n ?JS* lt ^ f r / re ?* 1 B J e af Minus ^ f Ori ^ nal Bleach 
1.000 (Specific Gravity of Water) 



18 BATES AND RUNYAN July 

Table VII may be used as a guide for determining the required 
amounts of solid chemicals. 

TABLE VII 

Bleach, Specific Gravity Film Bleach No. 713 

Original Specific Gravity 1 . 110 

At 5 Per cent Dilution 1.104 

At 10 Per cent Dilution 1 . 098 

At 15 Per cent Dilution 1 . 093 

At 20 Per cent Dilution 1 . 087 

At 25 Per cent Dilution 1 .081 

At 30 Per cent Dilution 1 .076 



4. Fixing-Bath Control 

No replenishment or rejuvenation is recommended for the No. 800 
fixer. Electrolytic methods of silver recovery are difficult to apply to 
neutral or alkaline fixing baths. It is recommended that the No. 800 
fixer be used until a silver concentration of about 2.5 grams per liter is 
reached or the time of clearing exceeds x /2 the total available fixing 
time. When this point is reached, the fixer solution should be re- 
placed by a fresh bath. The used solution may be treated with sul- 
fides to recover the silver. 

III. SUMMAKY OF TESTING OPERATIONS RECOMMENDED FOR 
CONTROL OF COLOR-PROCESSING LABORATORY 

A. Testing of Raw Materials 

The recommended raw material tests are tabulated in Table VIII. 
The frequency of tests will, of course, depend principally on the 
supply situation, size of shipments received, and number of manufac- 
turer's lot numbers involved. Emphasis should be placed on pretest- 
ing all lots of developing agents, sodium disulfite, and thiocyanate 
since variations in these chemicals are most likely to affect results. 
Less attention is required with the other chemicals once the consist- 
ency of a new source of supply has been ascertained. It is advisable to 
keep careful records of stock, date each chemical received, and date of 
its use for ready reference in tracking down variations in a solution mix. 

A thorough pretesting policy will often prevent bad solution mixes 
and reduce the possibility of machine slowdown because of solution 
supply. 



1949 



COLOR PROCESSING CONTROL 



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24 BATES AND RUNYAN July 

B. Testing of Solution Mixes 

The recommended tests for solution mixes are shown in Table IX. 
Considerable attention should be paid to pretesting solution mixes 
before they are placed on the machine. Unless errors of solution mix- 
ing or of previously unobserved chemical differences are detected at 
this point, quality of machine output will suffer. 

C. Testing During Machine Operation 

The tests indicated in Table X should be made at consistent inter- 
vals to provide a constant flow of information to the machine control 
chemist. 

In order to make correct decisions when photographic tests indicate 
trends away from normal, the control chemist should have at hand 
complete records of temperature and pH variations of all solutions as 
well as analysis of developers. 

ACKNOWLEDGMENTS 

The authors wish to acknowledge with thanks the assistance of 
Mrs. A. Reed and Mr. J. Kowalak in this work. The co-operation of 
Mr. A. Brunner in supplying analytical data has been very helpful. 

REFERENCES 

(1) M. H. Sweet, "Densitometry of modern reversible color film," J. Soc. Mot. 
Pict. Eng., vol. 44, pp. 419-436; June, 1945. 

(2) A. H. Brunner, Jr., P. B. Means, Jr., and R. H. Zappert, "Analysis of 
developers and bleach for Ansco color film," J. Soc. Mot. Pict. Eng., this issue, 
pp. 25-36. 

(3) J. L. Forrest, "Machine processing of 16-mm Ansco color film," /. Soc. 
Mot. Pict. Eng., vol. 45, pp. 313-327; November, 1945. 

(4) H. C. Harsh and K. Schadlich, "Laboratory for development work on color 
motion pictures," J. Soc. Mot. Pict. Eng., this issue, pp. 50-58. 

(5) R. M. Evans, W. T., Hanson, Jr., and P. K. Glasoe, "Iodide analysis in an 
MQ developer," J. Soc. Mot. Pict. Eng., vol. 38, pp. 180-188; February, 1942. 

(6) R. M. Evans, W. T. Hanson, Jr., and P. K. Glasoe, "Synthetic aged de- 
velopers by analysis," J. Soc. Mot. Pict. Eng., vol. 38, pp. 188-207; February, 
1942. 

(7) L. E. Varden and E. G. Seary, "Rapid test for ferricyanide bleach exhaus- 
tion," /. Soc. Mot. Pict. Eng., vol. 47, pp. 450-453; December, 1946. 



/Vnalysis of Developers and Bleach 
for Ansco Color Film* 

BY A. H. BRUNNER, JR., P. B. MEANS, JR., AND R. H. ZAPPERT 

ANSCO, BlNGHAMTON, NEW YORK 

Summary Published procedures for black-and-white developer analysis 
are reviewed. New analytical methods are described or old ones modified to 
achieve the accuracy required for the complete control of all constituents of the 
developers used for Ansco color film. To evaluate the bleach solution prior to 
regeneration, a procedure is presented for the determination of ferrocyanide 
ion in this solution. 

INTRODUCTION 

IT HAS BEEN RECOGNIZED for some time that the accurate analysis of 
black-and-white developing solutions is especially important in 
the control of continuously replenished developers. As shown by 
Bates and Runyan, 1 it is of even greater importance in color-processing 
developers because proper color balance must be maintained among 
three different emulsions. In the past few years, several articles have 
appeared in the technical literature concerning the analysis of black- 
and-white photographic developers, but nothing has been published 
on the analysis of developers used for processing color film because, 
until recently, color film was processed only by the manufacturer. 

Little has appeared in the literature concerning the control of 
photographic bleach solutions but when this solution is to be regen- 
erated, as described by Bates and Runyan, 1 a method for its analysis is 
necessary. 

The procedures here described are, for the most part, adaptations of 
methods previously reported for use with the usual black-and-white 
developers. They have been selected for their brevity, simplicity, and 
accuracy and have been used for the control of continuously replen- 
ished solutions for some time by unskilled technicians and require no 
special equipment other than a potentiometer. 

DISCUSSION 

The procedures discussed here have been adapted especially for use 
with the Ansco developers listed in Table I but may be used for other 
developers with some modification. 

* Presented May 18, 1948, at the SMPE Convention in Santa Monica. 

JULY, 1949 JOURNAL OF THE SMPE VOLUME 53 25 



26 BRUNNER, MEANS, AND ZAPPERT July 

TABLE I 
First Developer A-502 

Water, 65 to 90 degrees Fahrenheit 750 milliliters 

Metol 3 grams 

Sodium Sulfite 50 grams 

Hydroquinone 6 grains 

Sodium Carbonate Monohydrate 40 grams 

Sodium Thiocyanate 2 grams 

Potassium Bromide 2 grams 

Water to make 1 liter 

Color Developer A-605 

Water, 65 to 70 degrees Fahrenheit 750 milliliters 

Calgon 1 gram 

Sodium Bisulfite 2 grams 

Diethyl-p-Phenylenediamine Hydrochloride 4 grams 

Sodium Carbonate Monohydrate 67 . 5 grams 

Potassium Bromide 1 gram 

Water to make 1 liter 

Determination of Metol and Hydroquinone 

The first developer used in the Ansco color process is similar to the 
usual reversal first developer containing sodium thiocyanate. 

All the earlier methods for the determination of metol and hydro- 
quinone were based on two separate extractions of the developing 
agents and possessed several disadvantages, one of which was the de- 
termination of metol by difference. Baumbach 2 made a definite ad- 
vance in 1946 by describing a single methyl acetate extraction method 
involving a potentiometric acid titration of metol followed by oxida- 
tion of both metol and hydroquinone with iodine. Shaner and 
Sparks 3 modified this by using a U-tube extractor and methyl ethyl 
ketone as solvent. The difficulty in determining the end point in the 
iodine titration is a disadvantage common to both methods. When 
the pH is maintained at 6.5 to 7.0, the solution is so highly colored 
by oxidation products that it is extremely difficult to see the blue 
starch-iodine end-point. Oxidation at low pH values results in a 
nearly colorless solution, but the iodine oxidation is not quantitative. 

Because of the small sample used in the Shaner and Sparks proce- 
dure, the volume of acid needed to titrate the metol is very small. 
Four developers, cited by these authors, containing 2.0, 3.0, 0.22, and 
0.31 grams of metol per liter, require only 1.16, 1.74, 0.13, and 0.18 
milliliters of 0.1 normal acid when determined in accordance with their 



1949 COLOR FILM DEVELOPERS AND BLEACH 27 

procedure. Even if the procedure is changed and 0.05 normal acid is 
used, the volumes needed are still too small for reasonable accuracy 
with ordinary equipment. Moreover, with a sample of this size, the 
amount of metol present is too little to give a usable inflection in the 
titration curve. 

The disadvantage of the iodine titration may be avoided by oxidiz- 
ing the developers with eerie sulfate. Since this oxidation is per- 
formed in a strongly acid solution, highly colored oxidation products 
are not formed, and the end-point is easily observed. Stott 4 described 
a eerie sulfate titration to determine developing agents, but he de- 
termined the end-point potentiometrically. Use of the ortho-phenan- 
throline ferrous complex (ferroin) as indicator makes the titration 
simpler and faster since the color change is easily discernible. 

Equally satisfactory results have been obtained with methyl 
acetate, ethyl acetate, or isopropyl acetate as extracting solvent. 
With the methyl acetate used, a slight dark color appeared during the 
eerie sulfate titration which may be objectionable, but no such darken- 
ing occurred with the other two acetates. Methyl ethyl ketone, the 
solvent used by Shaner and Sparks, is itself oxidized by eerie sulfate, 
and therefore cannot be used. 

This modified Baumbach procedure involving the acid titration of 
metol and eerie sulfate oxidation of both metol and hydroquinone has 
been tested on developer A-502 with variation in the concentration of 
the developing agents from 50 per cent less to 20 per cent more than 
normal. Within this range, the metol determination was found to be 
accurate to 100.7 =*= 2.4 per cent and the hydroquinone to 99.5 =*= 1.5 
per cent. Occasional values above 100 per cent are probably due to 
mechanical carry-over of traces of developing solution with the solvent. 

Determination of Diethyl-p-phenylenediamine Hydrochloride 

Diethyl-p-phenylenediamine hydrochloride or its derivatives may 
be extracted in exactly the same manner as metol and hydroquinone. 
It may be titrated with acid the same as metol but since it is more 
basic and no hydroquinone is present, a better inflection point is ob- 
tained in the titration curve. It may also be oxidized with eerie sul- 
fate, and this oxidation using ferroin indicator is preferred to the 
potentiometric acid titration because it is faster and simpler. Im- 
mediately on addition of the eerie sulfate, a bright cherry red color is 
produced which is an intermediate oxidation product. The intensity 
of this color soon reaches a maximum, and then begins to fade until 



28 BRUNNER, MEANS, AND ZAPPERT July 

just before the end-point it disappears and is replaced by the same 
orange-pink indicator color observed in the metol-hydroquinone titra- 
tion. Another few drops of reagent produce the usual indicator color 
change. 

Determination of Sodium Sulfite and Bisulfite 

The bisulfite used in developer A-605 is converted to sulfite by the 
sodium carbonate. The same analytical procedure for the sulfite ion 
is, therefore, applicable to both developers. Atkinson and Shaner 5 
and Stott 4 have described a procedure in which an acidified standard 
icdine solution is titrated with the developer. This method may be 
used for these developers except that a weaker iodine solution should 
be used for developer A-605 since it contains a very small amount of 
sulfite ions. The only precaution required is that sufficient acid be 
present to keep the solution below pH 4 during the entire titration and 
thus prevent oxidation of the developing agents. 

This method was found to be accurate to 100.4 =t 2.0 per cent for 
concentrations ranging from 50 per cent less to 25 per cent more than 
the concentrations normally used. 

Determination of Sodium Carbonate 

Evans and Hanson 6 described a procedure in which carbon dioxide 
and sulfur dioxide are liberated by acidification of the developer, the 
sulfur dioxide is then oxidized to sulfate and the remaining carbon 
dioxide is measured volumetrically. Atkinson and Shaner 5 deter- 
mined carbon dioxide by absorption in soda lime or Ascarite. A 
simpler method described by Stott 4 involved the potentiometric titra- 
tion of the developer with standard acid using glass or platinum and 
calomel electrodes. In this titration, the first inflection point in the 
titration curve corresponds to the change of carbonate to bicarbonate, 
but because of the buffering action of the sulfite present, this inflection 
is not at all sharp. 

We have found it easier and faster to titrate the developer directly 
with standard acid to about pH 4 (gray color of methyl orange-indigo 
carmine) at which point the carbonate has been completely neu- 
tralized and the sulfite has been converted to bisulfite. By deducting 
the volume of acid required for the sulfite present, the carbonate con- 
tent may be calculated. Since developer A-605 has no alkalinity due 
to sulfite, no deduction is required. This method of determining car- 
bonate was found to be accurate to 99 == 1 per cent. 



1949 COLOR FILM DEVELOPERS AND BLEACH 29 

Determination of Potassium Bromide 

Since developer A-502 contains thiocyanate which behaves very 
similarly to bromide, a separation of the two must be effected. To de- 
termine bromide in the presence of chloride or thiocyanate, Atkinson 
and Shaner 5 recommended a rather lengthy iodometric procedure. To 
determine bromide in the presence of chloride, Stott 4 used the method 
of Evans, Hanson, and Glasoe 7 in which the developer was boiled, 
acidified, and boiled again, cooled, and titrated potentiometrically 
with silver nitrate using silver and calomel electrodes. This method 
cannot be used in the presence of thiocyanate because the boiling re- 
moves some but not all of the thiocyanate. 

Potassium bromide may be determined in developer A-502 in the 
range 1.0 to 3.5 grams per liter with an accuracy of 100.0 == 0.2 per 
cent by oxidation with 30 per cent hydrogen peroxide followed by the 
standard Volhard bromide procedure. 

Developer A-605 does not contain thiocyanate but does contain 
chloride ions from the color-developing agent which is added in the 
form of its hydrochloride. The method of Evans, Hanson, and Glasoe 7 
cited above gives satisfactory results, but it has been found that boil- 
ing, either before or after acidification, is unnecessary. After 
acidification, the bromide may be determined by potentiometric titra- 
tion with silver nitrate. Experience has shown that no advantage is 
gained by the addition of barium nitrate, sodium acetate, or alumi- 
num sulfate, as is sometimes recommended. The above procedure 
gave an accuracy of 100.0 =*= 0.5 per cent for concentrations of 1.0 to 
3.5 grams of potassium bromide per liter. 

Determination of Sodium Thiocyanate 

No method has been reported for the determination of thiocyanate 
in developers. Separation of thiocyanate from bromide is a lengthy 
procedure. Since the solubilities of silver thiocyanate and bromide are 
about the same, they are precipitated together and cannot be dif- 
ferentiated by the usual potentiometric titration. However, the sum 
of bromide and thiocyanate may be determined and, by deduction of 
the titer caused by the bromide, the thiocyanate concentration calcu- 
lated. The Volhard method cannot be used because the developing 
agents present reduce the ferric ion added as indicator. 

The sum of bromide and thiocyanate may be conveniently deter- 
mined by acidification of the developer and direct potentiometric 
titration with standard silver nitrate to the inflection point using 



30 



BRUNNEK, MEANS, AND ZAPPERT 



July 



silver wire and calomel electrodes (Fig. 1). With this procedure the 
thiocyanate was determined with an accuracy of 100 =t 1 per cent. 

Determination of Ferrocyanide in Bleach 
Ansco color bleach A-713 has the following composition: 
Dipotassium Mono Sodium Ferricyanide or Potas- 
sium Ferricyanide 100 Grams 

Potassium Bromide 15 Grams 

Dibasic Sodium Phosphate 40 Grams 

Sodium Bisulfate 25 Grams 

Water to make. . 1 Liter 



ML. O.IN SILVER NITRATE 
Fig. 1 Titration curve for bromide plus thiocyanate. 

During use some of the ferricyanide is reduced to ferrocyanide. 
Varden and Seary 8 described a colorimetric procedure for the rapid 
determination of color bleach exhaustion. When the bleach solution 
is to be regenerated with bromine as described by Bates and Runyan, 1 
the concentration of ferrocyanide must be determined more accurately 
than is possible with the colorimetric method. Standard textbooks on 
chemical analysis describe the determination of ferrocyanide in acid 
solution by tit ration with potassium permanganate or eerie sulfate. 
Either of these oxidants may be used with bleach A-713, but because 
of the deep color of the solution, the titration must be followed po- 
tentiometrically. In the permanganate titration, considerable time is 
required for the potential to reach equilibrium as the end-point is 



1949 



COLOR FILM DEVELOPERS AND BLEACH 



31 



approached. With eerie sulfate equilibrium is reached more rapidly 
and the length of time required for the titration is thus shortened. It is 
necessary that the sample be diluted as described since the position and 
magnitude of the inflection is influenced by the salt content of the solu- 
tion (Fig. 2). The eerie sulfate method gave an accuracy of 99.5 =*=0.5 
per cent in the range of 2.5 to 10.0 grams of ferrocyanide ion per liter. 

PROCEDURES 
Determination of Metol and Hydroquinone 

A. Metol Pipet a 25.0-milliliter sample of developer into a 125- 
milliliter separatory funnel. Add 2 drops of thymol blue indicator 



700 



600 



SAMPLE DILUTED l-l , 

INFLECTION AT 6.09ML. X 




SAMPLE DILUTED 1-4.6 
INFLECTION AT 8.21 ML. 



CALC. ENDPOINT 

8.2 4 ML. 



ML. O.IN CERIC SULFATE 
Fig. 2 Effect of dilution on titration of ferrocyanide in bleach. 

and one-to-one sulfuric acid until the color of the solution just turns 
yellow (pH 8 to 8.5). Add 12 grams potassium bromide, 25 milli- 
liters of iso-propyl acetate, shake for 3 minutes and then allow the 
layers to separate completely. Drain the aqueous layer into a 50- 
milliliter beaker, allowing a small amount of solvent to enter the stop- 
cock bore. Pour the solvent into a small dry beaker. Return the 
aqueous portion to the funnel, rinse the beaker with an additional 25 
milliliters of solvent and add this to the funnel. Repeat the shaking 
and separation. 

Pour the first solvent extract, containing most of the extracted 



32 BRUNNER, MEANS, AND ZAPPERT July 

developing agents, from the first to a second and to a third small dry 
beaker, and finally to a 400-milliliter beaker. After draining off the 
aqueous layer, pass the second portion of solvent through the same 
three small beakers to the 400-milliliter beaker. 

Add 100 milliliters of distilled water and 50 milliliters of methanol to 
the combined solvent layers and titrate potentiometrically with 
approximately 0.05 normal hydrochloric acid, using glass and calomel 
electrodes and mechanical stirring. Plot the titration curve of pH 
versus milliliters of acid and determine the inflection point. 

Grams of metol per liter = 

6.88 X milliliters of hydrochloric acid X normality of hydrochloric acid. 

B. Hydroquinone After the acid titration add 5 milliliters of one-to- 
one sulfuric acid and 2 drops of 0.025 molar ferroin indicator (o- 
phenanthroline ferrous complex). Titrate with approximately 0.1 
normal eerie sulfate solution, using mechanical stirring, until the 
pink-orange color changes to greenish yellow and remains changed for 
30 seconds. 

Grams of hydroquinone per liter = 

2.20 milliliters Ce(S0 4 ) 2 X normality Ce(S0 4 ) 2 - 

grams metol per liter"! 
3.44 J 

Determination of Diethyl-p-phenylenediamine Chloride 

A 25.0-milliliter sample of developer is extracted exactly as de- 
scribed in the procedure for metol. After the addition of 100 milliliters 
of distilled water, 50 milliliters of methanol, 5 milliliters of one-to-one 
sulfuric acid, and 2 drops of 0.025 molar ferroin indicator to the com- 
bined solvent layers, the solution is titrated with approximately 
0.1 normal eerie sulfate solution as described above. 

Grams of diethyl-p-phenylenediamine hydrochloride = 

4.01 X milliliters Ce(S0 4 ) 2 X normality Ce(S0 4 ) 2 . 

Determination of Sodium Sulfite in Developer A-502 

Place a portion of the developer in a 25-milliliter buret. Pipet 20.0 
milliliters of approximately 0.5 normal iodine solution into a 250- 



1949 



COLOR FILM DEVELOPERS AND BLEACH 



33 



milliliter Erlenmeyer flask containing 100 milliliters of distilled water 
and 5 milliliters of concentrated hydrochloric acid. Titrate the iodine 
solution with the developer until the iodine color is nearly discharged. 
Add 3 milliliters of starch solution and continue the titration until the 
solution becomes colorless. 

Grams of sodium sulfite per liter = 

milliliters of iodine X normality of iodine X 63 
milliliters developer required 

Determination of Sodium Bisulfite in Developer A-605 

Place a portion of the developer in a 25-milliliter buret. Pipet 5.0 
milliliters of approximately 0.1 normal iodine solution into a 250- 
milliliter Erlenmeyer flask containing 100 milliliters of distilled water 
and 5 milliliters of concentrated hydrochloric acid. Titrate the iodine 
solution with the developer until the iodine color is nearly discharged. 

idd 3 milliliters of starch solution and continue the titration until the 

>lution becomes colorless. 

Grams of sodium bisulfite per liter = 

milliliters of iodine X normality of iodine X 52 
milliliters developer required 

Determination of Sodium Carbonate 

Pipet a 20.0-milliliter sample of developer into a 250-milliliter 
Erlenmeyer flask containing 100 milliliters of distilled water and 4 
drops of methyl orange-indigo carmine indicator.* Titrate with 
approximately 1 normal hydrochloric acid to the gray end-point. 

Grams of sodium carbonate monohydrate per liter A-502 = 
milliliters HC1 X normality HC1 - (0.159 X grams Na 2 SO 3 per liter) 

0.323 

Grams of sodium carbonate monohydrate per liter A-605 = 
milliliters HC1 X normality HC1 
0.323 

* The mixed indicator is prepared by dissolving 0.1 gram methyl orange and 0.25 
gram indigo carmine in 100 milliliters of water. The end point is taken as the 
neutral gray color which occurs between the alkaline green and the acid violet 
shades. Bromphenol blue may be used in place of the mixed indicator, but the 
dichroic red-yellow end point is more difficult to see. 



34 BRUNNER, MEANS, AND ZAPPERT July 

Determination of Potassium Bromide in Developer A-502 

Pipet a 25.0-milliliter sample of developer into a 500 milliliter 
Erlenmeyer flask. Add 10 milliliters of 30 per cent hydrogen peroxide 
and warm gently until a vigorous reaction begins and then remove the 
source of heat. When the reaction has subsided, heat to boiling and 
boil for 3 minutes. Cool, add 100 milliliters of distilled water, and 
neutralize to alkacid paper by dropwise addition of one-to-one nitric 
acid and then add 5 milliliters in excess. 

Add 10.0 milliliters of approximately 0.1 normal silver nitrate from 
a pipet followed by 3 milliliters of saturated ferric ammonium sulfate 
solution which has been slightly acidified with nitric acid. (If desired 
10 milliliters of chloroform may be added and the solution well shaken 
to coagulate the precipitate.) Titrate with approximately 0.05 normal 
ammonium thiocyanate to the appearance of a dirty pink color which 
persists for 30 seconds. 

Grams of potassium bromide per liter = 

4.76 [(10 X normality AgNO 3 ) - 
(milliliters NH 4 SCN X normality NH 4 SCN)].- 

Determination of Potassium Bromide in Developer A-605 

Pipet a 50.0-milliliter sample of developer into a 400-milliliter 
beaker and neutralize to alkacid paper by the careful addition of one- 
to-one nitric acid, and then add about 5 milliliters in excess. Titrate 
potentiometrically with approximately 0.1 normal silver nitrate using 
silver and calomel electrodes. The end-point is the inflection in the 
curve of millivolts versus milliliters. 

Grams of potassium bromide per liter = 

2.38 X milliliters AgNO a X normality AgNO 3 . 

Determination of Sodium Thiocyanate in Developer A-502 

Pipet a 25.0-milliliter sample of developer into a 400-milliliter 
beaker containing 100 milliliters of distilled water. Add one-to-one 
sulfuric acid until the solution has a pH of about 2 and titrate potenti- 
ometrically with approximately 0.1 normal silver nitrate using silver 
and calomel electrodes. The end-point is the inflection in the curve 
of millivolts versus milliliters. 

Grams of sodium thiocyanate per liter = 

S^fmilliliters AgNOa X normality AgNO 3 - grai " S KBr PCT "H. 
L 4.76 



1949 COLOR FILM DEVELOPERS AND BLEACH 35 

Determination of Ferrocyanide in Bleach A-713 

Pipet 50.0 milliliters of bleach solution into a 400-milliliter beaker, 
add 20 milliliters of concentrated hydrochloric acid and dilute to about 
300 milliliters with distilled water. Titrate potentiometrically with 
approximately 0.1 normal eerie sulfate using platinum and calomel 
electrodes. Take the end-point as the inflection in the curve of 
millivolts versus milliliters or, in routine determinations, titrate to that 
millivolt reading which corresponds to the inflection point. 

Grams of ferrocyanide ion per liter = 

4.24 X milliliters Ce(SO 4 ) 2 X normality Ce(S0 4 ) 2 . 

ACKNOWLEDGMENT 

We wish to express our thanks to R. C. Johnston and C. A. Alfieri 
who assisted with the experimental work and to J. E. Bates and I. V. 
Runyan for their valuable suggestions. 

REFERENCES 

(1) J. E. Bates and I. V. Runyan, "Processing control procedures for Ansco 
color film," J. Soc. Mot. Pict. Eng., this issue, pp. 3-25. 

(2) H. L. Baumbach, "An improved method for the determination of hydro- 
quinone and metol in photographic developers," J. Soc. Mot. Pict. Eng., vol. 47, 
pp. 403-409; November, 1946. 

(3) V. C. Shaner and M. R. Sparks, "Application of methyl ethyl ketone to the 
analysis of developers for elon and hydroquinone," ./. Soc. Mot. Pict. Eng>, vol. 
47, pp. 409-418; November, 1946. 

(4) John G. Stott, "The application of potentiometric methods to developer 
analysis," J. Soc. Mot. Pict. Eng., vol. 39, pp. 37-55; July, 1942. 

(5) R. B. Atkinson and V. C. Shaner, "Chemical analysis of photographic de- 
velopers and fixing baths," /. Soc. Mot. Pict. Eng., vol. 34, pp. 485-524; May, 
1940. 

(6) R. M. Evans and W. T. Hanson, Jr., "Chemical analysis of an MQ de- 
veloper," J. Soc. Mot. Pict. Eng., vol. 32, pp. 307-321; March, 1939. 

(7) R. M. Evans, W. T. Hanson, Jr., and P. K. Glasoe, "Synthetic aged de- 
velopers by analysis," J. Soc. Mot. Pict. Eng., vol. 38, pp. 188-207; February, 
1942. 

(8) L. E. Varden and E. G. Seary, "Rapid test for ferricyanide bleach ex- 
haustion," J. Soc. Mot. PicL Eng., vol. 47, pp. 450-453; December, 1946. 



Note on an Improved Filter Holder 
for Color Printing* 

BY THEODORE J. BRAUN 

NAVAL PHOTOGRAPHIC CENTER, ANACOSTIA 20, D. C. 



Summary The modification of the printer head of a Bell and Howell 
Model J printer to accept filters for color printing is described. The novel 
location of the filters has the advantages of easy accessibility for quick inter- 
changing of filters, ability to use smaller size filters, and greatly increased 
filter life. 

INTRODUCTION 

WITH THE INCREASING USE of 16-mm color motion pictures by the 
United States Navy, it became necessary to find a better means 
of inserting optical niters in the light system of the Model J, 16-mm 
Bell and Howell printer. Previously, gelatin color-correction filters 
had been inserted in various positions in the lamphouse assembly. 
In these locations the filters soon buckled and faded, after short 
periods of operation. Various means of cooling the filters by in- 
creasing air circulation, by blowing compressed air, or by installation 
of fans have been attempted. However, in all such installations at- 
tempted, an inadequate filter life was obtained. 

The printer head was next considered as a possible location for 
the filters. (See Fig. 1.) The problem of placing the filters in the 
printer head consisted in making the filter holder lighttight, in order 
to stop all light rays except those which pass through the filter aper- 
ture, and yet not interfere with the mechanical operation of the 
printer. 

The problem of making the filter holder lighttight around its edges 
was accomplished by placing the filter-holder slide in contact with the 
inner surface of the printer-head housing and just clearing the aper- 
ture mechanism. The filter holder is made to just clear the main 
drive sprocket hub, and yet not allow extraneous light to pass around 
the end of the filter. 

A spring clip is provided to lock the filter holder in its proper posi- 
tion. (See Fig. 2.) The filter holder is constructed to allow different 

* Presented October 28, 1948, at the SMPE Convention in Washington. 
36 JULY, 1949 JOURNAL OF THE SMPE VOLUME 53 



FILTER HOLDER FOR COLOR PRINTING 



37 




Fig 1 Printer head with face plate removed. 

filter-pack combinations to be inserted quickly and easily. ( ee 
Fig. 3.) Additional holders may be provided to allow easy changes 
when emulsions requiring different filter balances are printed. 
Fig. 4 shows the filter holder being inserted into the printer-head 




Fig. 2 Filter inserted in face plate. 



38 



BRAUN 



July 




Fig. 3 Components of filter kolder. 

slot. The filter holder is equipped with a flange which is recessed into 
the printer-head face plate and is flush with the surface. This flange 
acts as a light trap over the slot and also determines the limit of 
travel of the filter holder into the printer head. 

Fig. 5 shows the filter holder in position for operation. In this 
position it does not interfere with the operation of the diaphragm 
light-changing mechanism. 

FILTER LIFE 

Location of the filters in the printer head, utilizes the present air- 
circulation system of the Bell and Howell printer to cool the filters. 




Fig. 4 Filter holder being inserted into printer head. 



1949 FILTER HOLDER FOR COLOR PRINTING 39 

Production runs with this filter device have been made over a period of 
days with little or no loss of color balance due to filter 
deterioration. 

Assuming a lamphouse filter arrangement, in which the filters are 
located 1.5 inches from the lamp as compared with 8 inches from the 
lamp in the present printer-head location of the filter, the intensity of 
illumination reaching the printer-head filter pack is approximately 
y 2 8 the intensity reaching a lamphouse filter pack. 




Fig. 5 Filter holder in operating position in printer head. 

ADVANTAGES 

1. In this location the filters are removed as far as possible from 
the light and heat of the light housing and from the heat of the 
standard heat-absorbing glass which is located in the lamphouse. 

2. Ability to change filter packs in a darkroom while the operator 
is in a sitting position without use of tools or without disassembly of 
the lamphousing. 

3. Freedom from distracting sounds of extra blower systems. 

4. Ability to insert an ultraviolet filter in the printing head for 
sound-track printing. 

5. Ability to print long-production runs without rapid filter de- 
terioration and consequent change of color balance. 

6. Ability to convert the Bell and Howell Model J printer to color 
printing at very low cost. 






Metallic- Salt Track on Ansco 
16-Mm Color Film* 

BY J. L. FORREST 

ANSCO, BINGHAMTON, NEW YOBK 



Summary In 16-mm Ansco color motion picture film the silver is removed 
from the image, leaving dye in the three layers. The combination (maximum 
density) of the subtractive colors has a visual density of about 3, which is 
sufficient to produce good screen contrast. The maximum density, while 
being visually opaque, has a transmission band in the near infrared in the 
region of 8000 angstrom units, which is the most sensitive region of the 
cesium-type phototube. While for many purposes this may not be objection- 
able, it can be overcome by differentially processing the film so that the 
sound-track modulations are opaque to red light without affecting the dye 
picture area. This paper describes a method by which differential treatment 
of the sound track area can be accomplished. 



THE METHOD OF PROCESSING Ansco color film has been presented 
in numerous publications and the procedure for machine processing 
of 16-mm Ansco color film has been presented. 1 In this process, the 
silver is removed from the image area, leaving dye in the three layers. 
The combination (maximum density) of the subtractive colors cyan, 
magenta, and yellow has a visual density of from 2.8 to 3, which is 
sufficient to produce good screen contrast. The maximum density, 
while being visually opaque, transmits the far-red and near-infrared 
radiation. 

A sound track on Ansco color film, processed in the usual way, is a 
dye track, the density of which is made up of the cyan, magenta, and 
yellow from the three layers. These dyes (Fig. 1) have good absorp- 
tion in the visible region of the spectrum, but transmit the far-red 
and infrared. If a track of this kind is played on sound-reproducing 
equipment utilizing a blue-sensitive phototube such as that described 
by Glover and Moore 2 (Fig. 2), the resulting volume will compare 
favorably with a silver track played on conventional equipment 
(Fig. 3). 

Most sound-projection equipment, however, uses a cesium-type 
phototube (Fig. 4). This applies particularly to 16-mm projectors. 

* Presented October 28, 1948, at the SMPE Convention in Washington. 
40 JULY, 1949 JOURNAL OF THE SMPE VOLUME 53 



METALLIC TRACK ON COLOR FILM 



41 



This tube has most of its sensitivity in the near infrared region of the 
spectrum. The dye track, therefore, is not so efficient as a metallic 
type of track for modulating a light beam from an incandescent source 
when read by a cesium-type phototube. 



3.0 
2.8 
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IS 
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6000 7000 

Wave/enjf/, 



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fl" 



Fig. 1 



Phototube 
Type S 4 



Wa^ Length fit 

Fig. 2 

The easiest and most direct approach to the solution of this prob- 
lem is to suggest the use of a blue-sensitive phototube. 3 " 6 Since it 
seems unlikely that a change-over to blue-sensitive phototubes will 
be made for some time, differential processing of the picture and sound 
track is necessary to make the sound-track modulations opaque to 
infrared light. Differential treatment of the sound-track area of 



42 



FORREST 



July 



motion picture film is not new to the motion picture industry. The 
patent literature 7 describes many procedures and methods for such 
treatments, each one more or less special and adapted to the process 



FREQUENCY C-PS 

** 

o o 






V 






B+W Or/7/W 

/fara 

Koda. C. hrome 

ftnsto Pye 




Fig. 3 



PhoTetukt. 






SOOO 6000 1000 30M 9000 1OOOO 11000 

Wave L mqth A' 



Fig. 4 



being used. All such processes involve special equipment and tech- 
niques which add extra steps to the processing procedure. Further- 
more, because the sound track must be confined to a definite area of 
the film specifically defined by established standards, 8 precision 



1949 



METALLIC TRACK ON COLOR FILM 



43 



application equipment is required and skilled technicians must be 
available to operate it. 

Patent literature 9 teaches that, in the case of Kodachrome, the 
sound-track area may be treated with a solution of a sulfide plus an 
iodide in order to retain the metallic salts in the sound-track area and 
thus increase its opacity to infrared light. 

A procedure for increasing the opacity of 16-mm Ansco color 
duplicating film to infrared light has been worked out in which the 
silver halides forming the modulations are converted to silver sulfide. 




Fig. 5 

This treatment produces a sound track on Ansco color film which' 
compares favorably in volume with a silver track when reproduced on 
the conventional red-sensitive phototube (Fig. 3) . Careful measure- 
ments have not shown any serious distortions introduced in the track 
by this treatment. Listening-test comparisions between a treated 
track and a silver track on a large number of samples indicated that 
there is a slight increase in noise level over the silver track, but in no 
case was this found sufficient to be judged objectionable. 

Unfortunately, the filter layer used in Ansco color film was found to 
contribute a slight stain to the clear area. The maximum absorption 



44 



FORREST 



July 



band of this stain, however, does not correspond to the peak of sensi- 
tivity of the cesium photo surface; therefore, it is not so objection- 
able as a visual inspection of the track might indicate. 

For reversible-type 16-mm film, the variable-area sound track is 
preferable and with a track treatment of this kind on reversible color 

film, the characteristics of the 
treated track lend it best to the 
variable-area method. 

For economical reasons, the 
procedure and equipment used 
for treating the film have been 
worked out to operate in con- 
nection with the Ansco color-film 
processing machines operating at 
the normal processing speed. The 
equipment can be used with any 
type of developing machine pro- 
viding a uniform steady film flow. 
A uniform flow of film through 
the equipment is absolutely es- 
sential for satisfactory results. 

In practice, since it is a rever- 
sal process, the sound track on 
Ansco color duplicating film is 
exposed from a positive-type 
track. A recorded track having 
characteristics favorable for 
printing on black-and-white re- 
versible duplicating stock will 
be suitable for printing on Ansco 
color duplicating film. After 
printing, the color film is proc- 
essed in the usual way up to 
the wash before the color developer. In the middle of this 
wash, the film is lead out of the wash into the sound-track 
treating equipment (Table I). In the sound-track-treating equip- 
ment, the film is first surface-dried to prevent creeping of the 
treating solution beyond the area allocated for the sound track. 
This drying is accomplished by passing the film through air squeegees 
(Fig. 5) and then into a small drying cabinet (Fig. 6). This drying 




Fig. 6 



1949 METALLIC TRACK ON COLOR FILM 45 

TABLE I 
ANSCO COLOR REVERSIBLE 16-MM SOUND-FILM PROCESS 





[i 


First Develop 


8-14 Minutes 




2 


Rinse 


5-10 Seconds 




3 


StOD . 


3 Minutes 


q 


4. 
5. 


Hardener 
Wash and Second 


3 Minutes 



Expose Approximately 2 Minutes 

Sound-Track Treatment > A. Feed to Edge-Treating Device 

B. Air Squeegee and Surface 

Dry 45-55 Seconds 

C. Edge-Treating Solution Ap- 

plication 

D. Reaction Time 15 Seconds 

E. Jet Wash (Track Downward) 

5 Seconds 

< F. Return to Color Processing 

Machine 

6. Finish Wash Approximately 1 Minute 

7. Coloi Develop 10-15 Minutes 

8. Rinse 5-10 Seconds 

9. Stop 3 Minutes 

10. Hardener 3 Minutes 

<u 11. Wash 3 Minutes 

12. Bleach 6 Minutes 

13. Wash 3 Minutes 

14. Fix 6 Minutes 

15. Wash 9 Minutes 

16. Dry 



requires about 50 seconds. From the drying chamber, the film is lead 
over the applicator roller and here the edge-treating solution is 
applied to the track area (Fig. 7) . The reaction of the solution is very 
rapid; only about 15 seconds are required to convert the silver halides 
in the track to silver sulfide. The treating solution is essentially an 
aqueous solution of sodium sulfide with Cellosize WS-100 (hydroxy- 
ethyl cellulose) added to increase the viscosity (Table II) . After this 

TABLE II 
EDGE-TREATMENT SOLUTION FORMULA 

Cellosize WS-100 100 Cubic Centimeters 

Sodium Sulfide (Anhydrous) 20 Grams 

Water to make. . , 1 Liter 



46 



FORREST 



July 



reaction, the excess solution is washed off the track area and the film is 
returned to the wash tank from which it was taken. This entire 
treatment requires about 75 seconds. After its return to the wash tank, 
the film continues on through the rest of the process in the usual way. 
Although this process of treating the track requires care, it is a 
straightforward procedure and is not untidy or odorous. The solu- 
tion contains sodium sulfide; however, the amount of solution re- 
quired is small, only about 10 cubic centimeters or 1 / s ounce is 
required for 100 feet of film. Therefore, the handling of the solution 




Fig. 7 



presents no problem or hazards in the processing laboratory if ordi- 
nary precautions are taken. 

The unit is compact and portable on casters (Fig. 8) and when used, 
it is moved alongside the developing machine and remains there 
through the run. Even for developing machines continuously proces- 
sing sound film, the portable construction is desirable. This type of 
construction makes it possible to move the unit out of the way to give 
free access to the processing machine for maintenance and cleaning. 

The unit itself does not propel the film. This is accomplished 



1949 



METALLIC TRACK ON COLOR FILM 



47 



entirely by the processing machine. Actually, the processing ma- 
chine pulls the film through the sound-track-treating unit. In order 
that no undue strain be placed on 'the film, the sound-track-treating 
unit is tendency-driven, that is, the shafts in the rollers of the drying 
cabinet are turning in loose rollers. After leaving the drying cabinet, 
the film is fed over a roller cluster to guide it accurately over the edge- 
treating roller (Fig. 7). Here, the sound-track area comes in con- 




Fig. 8 

tact with a bead of the edge-treating solution carried on the slightly 
concave periphery of the applicator wheel. The bead wheel travels 
at a slightly faster rate of speed than the film and in the same direc- 
tions as the film. This maintains a uniform bead in contact with the 
track area. 

The amount of solution applied is controlled by the depth of dip of 
the applicator wheel in the solution, and lateral movement of the 
wheel is controlled by two micrometer adjustments on the applicator 
assembly. With these adjustments, no difficulty has been ex- 
perienced in confining the track area within the established standard. 



48 



FORREST 



July 



After edge-treating, the solution is allowed to react for 15 seconds and 
is then removed by a special spray washing the excess solution off the 
track area (Fig. 9). From this point, the film is returned to the 
processing machine and continues on through the rest of the process in 
the usual way. 

Sound tracks processed in this way are permanent and are no more 
subject to scratches and abrasions than normal silver sound tracks 
made on black-and-white film. Any subsequent treatment, such as 
lacquering or waxing, which can be applied safely to the color film, will 
not harm the treated sound track. 




Fig. 9 



REFERENCES 

(1) J. L. Forrest, "Machine processing of 16-mm Ansco color film," J. Soc. 
Mot. Pict. Eng., vol. 45, pp. 313-327; November, 1945. 

(2) A. M. Glover and A. R. Moore, "A phototube for dye image sound track," 
/. Soc. Mot. Pict. Eng., vol. 46, pp. 379-387; May, 1946. 

(3) Glover and Jones, "A new high sensitive photo-surface," Electronics, 
August, 1940. 

(4) R. O. Drew and S. W. Johnson, "Preliminary sound track tests with vari- 
able-area dye tracks," J. Soc. Mot. Pict. Eng., vol. 46, pp. 387-405; May, 1946. 

(5) R. Gorisch and P. Gorlich, "Reproduction of color film sound records," 
,/. Soc. Mot. Pict. Eng., vol. 43, pp. 206-214; September, 1944. 



1949 



METALLIC TRACK ON COLOR FILM 



49 



(6) Schinzell, Kinotechnik, p. 464, 1929. 

(7) U.S. Patents 2,143,787; 1,973,463; and 2,330, 796. 

(8) ASA Standard Z52. 16-1944 or succeeding Standard. 

(9) U. S. Patent 2,258,976. 

DISCUSSION 

MR. EARL I. SPONABLE: What material do you use for making the applicator 
disk? 

MR. J. L. FORREST: Stainless steel. 

MR. R. T. VAN NIMAN: Has this process been worked out for application to 
35-mm film yet? 

MR. FORREST: I have not used it with 35-mm although there is no reason 
why it could not be used. 

MR. C. R. KEITH: Do you have any figures of the over-all gamma of the 
sulfide track in terms of the light used in reproducing it? 

MR. FORREST: The data are being collected now but are not ready at this time. 



FORTY-ONE YEARS AGO 

Open-Air Theater in Jacksonville, Fla. 

The opening of the Summer season at Dixieland Park proved a re- 
markable success. In the afternoon fully 1500 people visited the park 
and enjoyed the concert, but it was in the evening that the big crowd 
turned out to see the open-air moving pictures. 

At least 2500 people were on the grounds before eight o'clock, and the 
seating capacity, which had been arranged for 2000, proved entirely in- 
adequate. Manager Da Costa and several of the directors were present, 
and it was at once decided to arrange seats for at least 1000 more people. 

The pictures started promptly at 7:30, and were very good. They 
could be seen nicely at a distance of 1000 feet from the elevated canvas, 
and were thoroughly enjoyed by the immense audience. The full 3000 
feet of films were run and the entertainment lasted a little over an hour. 

The Moving Picture World, May 16, 1908 



Laboratory for Development Work 
on Color Motion Pictures 

BY H. C. HARSH AND K. SCHADLICH 

, BlNGHAMTON, NEW YORK 



Summary Precise control of all of the laboratory operations in producing 
color motion pictures is essential to obtain release prints of high quality. A 
description is given of a new building and equipment especially designed to 
carry on development work on all the laboratory phases of producing motion 
pictures in Ansco color. 



COLOR-FILM MATERIALS f or the professional motion picture industry 
have to meet a number of exacting requirements. In the case of 
multilayer color materials many of these properties have to be already 
incorporated in the film. However, of equal importance is the proper 
processing of these materials and the requirements which are of par- 
ticular importance can be summarized as follows : 

1. Steadiness of the color image, free from processing fluctuations, 

streaks, and processing shimmer. 

2. Methods for the preparation of dupes for optical effects, process 

photography, and protection masters. 

3. Good sound reproduction. 

In order to solve these well-recognized problems, a new laboratory 
was completed during 1948 which will be described briefly in this 
paper. Its facilities are used primarily to carry out development 
work on new and improved 35-mm color films and all aspects connected 
with the processing and use of these materials. The laboratory will 
provide technical assistance and data to commercial laboratories 
which are now processing and printing Ansco color films and serve 
as a source of information for those who are planning to set up a 
laboratory for this purpose. 

The building, which is constructed of reinforced concrete and brick 
is 40 by 80 feet and is attached to a larger building which is now used 
as a finished goods warehouse but which is being converted entirely 
for research and development purposes. 

* Presented May 18, 1948, at the SMPE Convention in Santa Monica. 
60 JULY, 1949 JOURNAL OF THE SMPE VOLUME 53 



COLOR LABORATORY 





51 




FIRST FLOO"R PLAN 

Fig. 1 



Fig. 1 shows the plan of the first floor which includes two rooms for 
the processing machine, rooms for reeling, optical printing, release 
printing, sound testing, and editing as well as office space. 

Fig. 2 shows the plan of the second floor which includes the solu- 
tion-mixing room, control laboratory, air conditioning, office space, 
film vault, projection booth, and review room. 

PROCESSING MACHINE 
It was realized that the success of this pilot installation would be 




SECOND "FLOOR PLAN 

Fig. 2 



52 



HARSH AND SCHADLICH 



July 



dependent to a great extent on the quality of processing which could 
be realized and the flexibility of the machine for experimental changes. 
In order to obtain a smooth screen quality every attempt has been 
made to provide the optimum developer turbulence conditions based 
on the available experience from the industry and consistent with 
other requirements. 

The basic design is the same as the Ansco 4C 16-mm color machine 
described by Forrest. 1 Substitution of 35-mm spools results in a 




Fig. 3 White-light section of processing machine. 

lower machine speed of 30 feet per minute which for experimental 
purposes is quite adequate. The bottom-friction-drive principle, com- 
bined with an underdriving take-up spool, provides a smooth motion 
of the film through the machine which is very important for effective 
use of the high-pressure jet agitation system which will be described 
below. 

The first section of the machine consists of the elevator and seven 
spool banks in four tanks. This section accommodates the first 
development, short stop, and hardening steps of reversal processing 
and when in operation is in no light. A lighttight pass box is 



1949 



COLOR LABORATORY 



53 



provided between this room and the next which comprises the white- 
light section. In this section there are nineteen spool banks in 
twelve tanks which comprise the color development, short stop, hard- 
ening bleach, fixing and the several washing steps, followed by the 
drying cabinet. 

Fig. 3 shows a side view of the white-light section of the machine 
with the spool banks partially raised. The wall on the west or operat- 



DETA-IL OF JET 




JETS l"X'/32" GR/rjCC 

*//,'' rfloft r-ii~w 

288 JETS, IN 1ST T>EV (4 BANKS) 

3feO X6TS IN COLOR DCV. (.f BANKS) 

PUMPS 7 '/2. U. "P. 

fP TO /2 LBS V SI. 

/^OW UT> TO SOO GflLS /MI/V. 

BACK UP 

flotcr /?s STAINLESS 



Fig. 4 Schematic of jet arrangement. 

ing side of the machine carries the control switches and recording 
instruments. The adjacent wall, near the pass box, partially visible 
in Fig. 3, supports the valves and flow meters which control the con- 
tinuous replenishment of the developers, short stops, and hardeners. 
An important new feature of this machine is the high-pressure jet 
turbulation which has been provided in both developers. A manifold 
coming into the top side of the tank supplies six jet tubes per spool 
bank. A cross-section schematic diagram of the jet arrangement on 



54 



HARSH AND SCHADLICH 



July 



each bank is shown in Fig. 4. The jets are Vie inch from the film sur- 
face and opposite each jet tube are cloth-covered back-up rollers to 
support the film. It is important that the jets are regularly spaced 
and in this case the film passes a jet every 2 x /2 seconds. The jet 
orifice is 1 X l /sz inch. The two pumps have 7V2-horsepower motors 
which supply up to 12 pounds pressure at the jet an4 circulate the 
solution at the rate of 500 gallons per minute. 









Fig. 5 Sensitometric strip to measure bromide drag. 

To the best of our knowledge, this is the first time that high-pres- 
sure jet turbulation has been used effectively on a bottom-friction- 
drive machine. As mentioned earlier, it is possible because of the 
uniform motion of the film. 




V 



NO JE.T 
AGITATION 



JET EVtflV 
7 SECONDS 



JET C.VCRV 
2'/i .JCCO.VDS 



Fig. 6 Graphs showing effect of jet agitation. 

The importance of adequate turbulence in processing color film can 
be demonstrated easily. For example, let us consider its effect in 
eliminating bromide drag. In Fig. 5 a type of sensitometric strip is 
shown which is designed to measure this effect quantitatively. The 
opposite circular areas receive equal exposures but in one case the 
immediate surrounding area receives maximum exposure and in the 
other the immediate surrounding area receives no exposure. The 
difference in the measured densities of the circular areas after proc- 
essing gives a good quantitative evaluation of the efficiency of the 



1949 



COLOR LABORATORY 



55 



processing in eliminating bromide drag. Fig. 6 shows sensitometric 
curves for the cyan layer of Ansco Color Type 735. The set of curves 
marked A were those obtained without using the jets and the dotted 
curve represents the exposures having the dark surrounding area. 
The second set of curves marked B shows the improvement obtained 
when only two jet tubes per spool bank at 10 pounds pressure are 
used. Finally, the set of curves marked (7, with all the jets in use at 
4 pounds pressure, are nearly coincident at all densities, which is the 
desired result for good screen quality. The effect in the magenta and 
yellow layers is similar although with inadequate agitation the dif- 
ference is not so great as with the cyan layer. This result would be 
expected since the latter is at the bottom of the monopack. 

Agitation is also used in the bleach, short stops, and fixer although 
the high pressure and frequency of jets as described for the developers 
is not necessary in these cases. Agitation of the short stops is very 
important for eliminating processing streaks and shimmer and in this 
installation the short stops are agitated by bubbling air through the 
tanks. For the bleach and fixer, single low-pressure jets without 
back-up rollers are located in the center of the tanks. For washing, 
nozzle sprays are used and have been found more efficient than full 
tanks. 

The filters, jet and circulation pumps, air compressor, filter for the 
wash water, and other units are located in the basement under the 
machine. 

The solution mixing room is located on the second floor directly 
above the front end of the machine. Seven stainless-steel mixing 
tanks, two small stoneware tanks, and a sink are located over this 
area with an operating platform in the center. The plumbing from 
these tanks to the machine is through black Seran pipe. 

Six of the stainless-steel mixing tanks are used to supply the first 
developer, short stop, hardener, color developer, bleach, and fixer. 
The seventh tank is a spare connected to the color developer system. 
The two stoneware tanks are arranged so that they can supply solu- 
tion to any machine tank through a utility line with flexible couplings. 

By closing two valves the circulating pumps can be used to return 
the first developer, color developer, and bleach from the machine to 
their mixing tanks. This feature has proved expedient in experi- 
mental work and is convenient for maintenance and cleanup. In the 
case of the bleach, it is the most desirable procedure for carrying 
out the replenishment. 



56 



HARSH AND SCHADLICH 



July 



An exhaust system removes fumes from the color developer and 
bleach-mixing tanks. 

CONTROL LABORATORY 

The control laboratory, which is located next to the mixing room, is 
equipped to carry out the control procedures and chemical analyses 
described in the papers by Bates and Runyan 2 and Brunner, Means, 
and Zappert. 3 





Fig. 7 Photograph from front of review room. 



PRINTING 

Standard equipment with slight modification is used for optical 
and release printing. An Acme optical printer is used for printing 
masked duplicates and special effects. The basic features of this 
printer have been described by Dunn. 4 A Bell and Howell Model D, 
modified with an optical system for increased illumination and with a 
filter-change devise for scene-to-scene correction, is used for printing. 

SOUND TESTING 
The equipment for sound testing, which has not yet been installed, 



1949 COLOR LABORATORY 57 

will include complete channels for recording and re-recording variable- 
area and variable-density tracks and the necessary accessory instru- 
ments for measurements. 

PROJECTION ROOM 

The projector is a standard Super-Simplex E7. Because of the 
relatively short throw, wire screens are used in the light beam to re- 
duce the screen brightness to I0 l /z foot-lamberts. 

A photograph taken from the front of the review room is shown in 
Fig. 7. For the acoustical treatment of the walls and ceiling, per- 
forated panels of Johns-Manville gray Transite backed up with rock 
wool are arranged appropriately with unperf orated panels of the same 
material. The floor is carpeted to within 1 1 feet of the screen. Live 
sections in the front of the room are provided in order to give the opti- 
mum results at the rear three rows of seats. Measurement of the 
reverberation time as a check on the efficiency of the design gave 
results very close to the desired theoretical values. 

REFERENCES 

(1) J. L. Forrest, "Machine processing of 16-mm Ansco color film," J. Soc. Mot. 
Pict. Eng., vol. 45, pp. 313-327; November, 1945. 

(2) J. E. Bates and I. V. Runyan, "Processing control procedures for Ansco 
color film," J. Soc. Mot. Pict. Eng., this issue, pp. 3-25. 

(3) A. H. Brunner, Jr., P. B. Means, Jr., and R. H. Zappert, "Analysis of de- 
velopers and bleach for Ansco color film," J. Soc. Mot. Pict. Eng., this issue, pp. 25- 
36. 

(4) L. S. Dunn, "The new Acme-Dunn optical printer," J. Soc. Mot. Pict. Eng., 
vol. 42, pp. 204-211; April, 1944. 



1000-Foot Bipack Magazine 
and Adapter* 

BY WILTON R. HOLM AND JAMES W. KAYLOR 
CINECOLOR CORPORATION, BURBANK, CALIFORNIA 



Summary Users of 35-mm bipack film have been restricted to the use of 
400-foot rolls of negative stock. This is because present standard photo- 
graphic equipment will not handle 1000-foot rolls in the conventional-type 
bipack magazine. Loss of production time and excessive negative wastage, as 
well as severe photographic limitations, are the result. 

An adapter has been developed at Cinecolor Corporation which permits the 
use of 1000-foot rolls of negative film in side-by-side position, rather than 
one over the other. This arrangement gives an attractive and convenient 
operating assembly, which keeps the center of gravity low. It eliminates the 
need for unwieldy and top-heavy blimps. The adapter causes the films to be 
changed from a side-by-side to the superimposed emulsion-to-emulsion re- 
lationship required in bipack photography. In the Cinecolor arrangement, 
the 1000-foot rolls are fed from a single 70-mm magazine into the adapter. 
Two individual 1000-foot magazines can be used equally well. 



PRODUCERS OF FEATURE PHOTOPLAYS in a two-color process, using 
35-mm bipack as a photographing medium, are restricted to 400- 
foot lengths of picture negative film. Many disadvantages, both 
artistic and economic, are attendant upon this limitation. It is im- 
possible to photograph a scene longer than 400 feet, and directors 
often want longer master scenes. Likewise, it is impossible to retake 
a scene longer than 200 feet without pausing to reload the camera. 
Often it becomes extremely difficult to obtain the desired dramatic 
interpretation of a scene when it is necessary to stop and reload after 
every take. From an economic point of view, this excessive reloading 
time represents a loss of valuable production time. An additional 
economic factor is one of excessive picture negative wastage, because 
of the number of rather long "short ends" which accumulate. 1 

Bipack picture negative film is manufactured in 400-foot, rather 
than the customary 1000-foot lengths, only because all commercially 
available bipack magazines for production-type cameras have a 
capacity of 400 feet. This is perhaps because bipack photography has 
developed around the use of existing black-and-white equipment. 

* Presented May 18, 1948, at the SMPE Convention in Santa Monica. 
58 JULY 1949 JOURNAL OP THE SMPE VOLUME 53 



BIPACK MAGAZINE 



59 



Since the demand was not great, the bipack magazine evolved with a 
minimum of modification and design expense, resulting in the over- 
and-under type of magazine, which has persisted to the present 
time. 

In effect, the over-and-under-type bipack magazine is a unit made 
up of two conventional magazines, one mounted on top of the other. 
Such a magazine is shown in Fig. 1. The upper section contains the 
panchromatic film; the front spool is the supply spool, and the rear 
spool the take-up spool. The lower section contains the orthochro- 
matic film, and, as in the case of the "pan" section, the front spool is 
the supply spool and the rear spool the take-up spool. 



PAN SUPPLY 




PAN TAKEUP 



ORTHO 

TAKE UP 



Fig. 1 

As is well known to users of bipack film, a bipack is composed of 
two separate strips of film. One, the orthochromatic, records the 
blue and part of the green components of the scene to be photo- 
graphed; the other, the panchromatic, records the red and the re- 
maining green components. In bipack photography, the exposure is 
made with the two films in emulsion-to-emulsion superimposed rela- 
tionship, with the orthochromatic emulsion nearest the lens. Thus the 
exposure is made through the base of the orthochromatic film. When 
using the over-and-under type magazine, the panchromatic film 
travels from the forward, or supply spool of the upper section, down 
into the lower section. The panchromatic film is wound "emulsion 
in" on the supply spool and travels down into the lower section with 
the emulsion side facing the lens. Here it is joined by the ortho- 
chromatic film, which is wound "emulsion out" on the supply spool. 



60 



HOLM AND KAYLOR 



July 



As the orthochromatic film unwinds, it thus moves into the required 
emulsion-to-emulsion superimposed relationship with the panchro- 
matic film, with the orthochromatic film nearest the lens (Fig. 1). 
The films now travel together down into the camera. After exposure 
the films travel up out of the camera into the lower section of the 
magazine. Here the orthochromatic film is rewound onto the "ortho" 
take-up spool, while the panchromatic film continues up into the up- 
per section of the magazine where it, in turn, is rewound onto the 
"pan" take-up spool. 




Fig. 2 

It can easily be visualized that such an over-and-under magazine of 
1000-foot capacity would be an extremely ungainly and inconvenient 
camera assembly, having a high center of gravity. This, in turn, 
necessitates the use of cumbersome, top-heavy blimps. 

An adapter has been developed which permits the use of 1000-foot 
rolls of negative picture film in a side-by-side, rather than an over-and- 
under position. Two standard 1000-foot capacity, 35-mm magazines, 
or one double width (70-mm) magazine of 1000-foot capacity, can be 
mounted on top of the adapter to hold two 1000-foot rolls of film. The 
70-mm magazine is used here in describing the operation of the 
adapter. 

The orthochromatic film (0) and the panchromatic film (P) emerge 



1949 



BIPACK MAGAZINE 



61 



from the magazine (1) and enter the adapter (2) in a coplanar, side- 
by-side relationship, as shown in Fig. 2. The orthochromatic film 
is wound emulsion side out, and the panchromatic film emulsion side 
in, on the supply spools. In the adapter the films are superimposed to 
bring them into emulsion-to-emulsion relationship, with the ortho- 
chromatic film nearest the lens. This superimposition is accomplished 
by looping and laterally displacing the orthochromatic film as shown 




Fig. 3 

(Fig. 2). In this relationship the films emerge from the adapter and 
enter the camera. After exposure the films return to the adapter, 
where they are separated by again looping and laterally displacing the 
orthochromatic film, and returned to a coplanar, side-by-side rela- 
tionship. In this manner they emerge from the adapter and enter the 
magazine, where they are wound onto take-up spools. 

The translatory loops are maintained in the adapter by means of 
an idler shaft carrying two concentric sprocket guides (4)- Sprockets 
(3) are mounted on either side on a member which pivots to permit 






62 



HOLM AND KAYLOR 



July 



threading the film in the adapter. When in operating position, the 
sprockets are locked in contact with the guide rollers. 

As is customary, only the take-up reels are driven. The supply 
reels are rotated by removal of the film, and since the speed of the 
take-up reel varies with the amount of film wound on the reel, a 
clutch is needed between the driving power and the reel to allow for 
overdriving, and to compensate for possible differences in length be- 
tween two rolls of negative film. 




Fig. 4 

A clutching device was desired which would not be too bulky, and 
would not overhang the camera outside the magazine. It was also 
desired that the clutch should not be completely enclosed within the 
magazine, thus making it impossible to adjust without opening the 
magazine. A pair of single-disk clutches within the take-up spool, 
arranged coaxially on the same shaft, was designed to meet these re- 
quirements. Ball-bearing surfaces reduce friction and increase the 
life of the drive. 






1949 BIPACK MAGAZINE 63 

The adapter-and-magazine unit has been extremely satisfactory in 
all tests. Runs of 1000 feet with no stops were made using a "wild" 
motor at an ambient temperature as high as 110 degrees Fahrenheit, 
without undue heating of the motor. During tests made at low tem- 
peratures (0 to 15 degrees Fahrenheit) the unit operated perfectly 
when it was so cold as to make it difficult to rack over the camera. 
In all tests made to date, the unit has never failed. 

Tests run to date indicate that the unit is no more noisy than the 
standard 400-foot bipack magazine. Provisions have been made, 
nevertheless, for additional soundproofing of the adapter, should this 
be required. In order to use the unit with a standard blimp, it is only 
necessary to fabricate a slightly taller top for the blimp, an inex- 
pensive and easy-to-do modification. This top can then be used in- 
terchangeably with the standard top permitting the blimp to be used 
either for color or black-and-white. The new blimp tops are being 
made at the present time, and it is expected that the 1000-foot maga- 
zine and adapter units will be in production use in the very near 
future. 

Figs. 3 and 4 show the unit set up for operation. 

REFERENCE 

(1) J. W. Boyle and B. Berg, "Studio production with two-color bipack motion 
picture film," /. Soc. Mot. PicL Eng., vol. 48, pp. 111-116; February, 1947. 



FORTY-ONE YEARS AGO 

Middleport Frowns on Moving Picture Shows 

Middleport, N. Y., May 1. An edict has been passed by the city 
fathers of Middleport that moving picture shows are a menace to 
women and children who patronize them, and, consequently, all efforts 
of a party of Medina men to establish a nickelodeon here within the 
past few days have failed. 

The Moving Picture World, May 16, 1908 



Cathode- Ray-Tube Applications 
in Photography and Optics* 

BY CARL BERKLEY AND RUDOLF FELDT 

ALLEN B. DuMoNT LABORATORIES, CLIFTON, NEW JERSEY 

Summary Cathode-ray tubes and oscillographs are ideal tools for the 
solution of many technical problems in the related arts of photography and 
optics. The methods described represent typical examples of the application 
of electronic-measurement techniques in such fields. 

Applications considered and illustrated include: 

1. Gloss measurement on photographic papers. 

2. Goniophotometry of light sources. 

3. Shutter, flashbulb, and synchronizer testing. 

4. Cathode-ray-tube light sources for facsimile and stroboscopic work. 

5. Scanning technique for television motion picture recording. 

6. The combination of optical and electronic magnification for the study 
of gear and sprocket imperfections. 

7. Automatic H and D curve plotting during film development. 

8. Cathode-ray-tube sound on film recording systems. 

9. The measurement of ripple in light sources. 

10. Color studies in natural color reproduction and chromatic aberration in 
lenses. 

1 1 . Vibration studies of motion picture equipment. 

The techniques and cathode-ray oscillograph accessories described will 
find wide application in other fields as well. 

MAINLY BECAUSE OF its rapid response and graphic presentation 
of results, the cathode-ray oscillograph has found wide appli- 
cation in the solution of many technical problems in diverse fields. In 
the course of their work, the authors and the members of the Appli- 
cations Engineering Section of DuMont Laboratories have gained 
considerable experience in the application of the basic oscillographic 
techniques used in the solution of these problems. Since photo- 
graphic and optical methods have become increasingly important in 
oscillography, a surprising proportion of the applications studies at 
the Laboratories have been in these fields. The techniques here 
described for photography and optics are basic and applicable to a 
much wider range of problems. To illustrate this point, it will be 
shown that many of the methods herein described will find direct 
application in the automotive industry. It is therefore felt that 

* Presented November 5, 1948, at the National Electronics Conference, Chicago. 

Published in Electronic Engineering (England). 

64 JUNE, 1949 JOURNAL OF THE SMPE VOLUME 52 



C-R-TuBE APPLICATIONS 65 

their description will be on interest and help to anyone concerned 
with a precise electronic approach to a measurement problem. 

SHUTTER, FLASHBULB, AND SYNCHRONIZER TESTING 

One of the basic problems in photography as in many other indus- 
tries is that of accurate short-interval timing. Photographic shutters 
are called upon to operate reliably and reproducibly over a wide range 
of speeds. Synchronizers and flashbulbs must be timed to operate 
within milliseconds of one another. This problem of proper adjust- 
ment is becoming more important with the increasing use of color 
films whose latitude does not tolerate the careless operation to which 
photographers using monochrome emulsions have become accustomed. 

SHUTTER TESTING 

The obvious way to study and make these adjustments is by 
picking up the opening of the shutter by means of a phototube and 
light and displaying its output on an oscillograph. This procedure, 
was, in fact, tried many years ago using a string or mirror oscillo- 
graph with fairly satisfactory results. 1 

There are a number of advantages to be gained by the use of a 
cathode-ray oscillograph : 

1. There is no practical limit on the shortest time that can be 
measured so that high-speed mechanical shutters or electrooptical 
shutters can readily be studied. 

2. The image of the shutter characteristic appears instantaneously 
on the face of the cathode-ray tube, so that no waiting is necessary 
to view the record. 

3. The shutter may be operated rapidly any number of times in 
succession, synchronized with the single sweep on the oscillograph, 
and any erratic operation easily observed by comparing each pattern 
with the previous one by means of a long-persistence cathode-ray- 
tube screen; by operating the shutter a few times and then observing 
the persistent image, an average value for the shutter speed may be 
obtained. This is of value in the case of simple shutters whose re- 
producibility is not such that a single reading suffices for calibration. 

6. Various other electronic methods of testing camera shutters 
have been devised. These generally involve integrating the total 
light transmitted during the operation of the shutter, and expressing 
the result as a single reading on a meter. Such a reading fails to show 
any erratic operation of the shutter such as bouncing or slow opening 



66 



BERKLEY AND FELDT 



July 



and closing which, while it may give rise to the same integrated value 
of light, represents improper operation of the shutter. Such im- 
proper operation is readily displayed on the cathode-ray tube. 

Realizing all these advantages, many photographers today have 
devised elaborate oscillographic equipment to enable production 
testing of shutters. 2 " 9 Such equipments are now being used by most 
camera manufacturers to check their shutter operation. 



I 1 I 1 |l! I j 

III! ','H 

mi 

UN 

nil 



II;! I I 
If 

r t I I i 



I i I i i 
I 111 






tliii 

i i i i 



Fig. 1 Focal-plane shutter characteristics. Shutter speed Vso second on a 

Graflex shutter horizontal sweep approximately 1 / 2 o second, 
(a) With low-frequency sweep approximately 600 cycles to show principle. 

Our previous remarks have all referred to the testing of between- 
the-lens leaf -type shutters. The cathode-ray oscillograph has also 
been applied successfully to the testing of focal plant shutters by 
a technique described by Bullock. 2 This technique involves the 
photographing of a vertical oscillator trace on the cathode-ray tube 
and the sweep of this trace horizontally across the cathode-ray tube 
for a time somewhat longer than the operation time of the shutter. 
This pattern is then imaged in the focal plane. The sum of the 
cathode-ray-tube spot and focal-plane slit motions gives rise to 



1949 C-R-TuBE APPLICATIONS 67 

diagonal areas from whose appearance the shutter opening character- 
istics may be evaluated. Figs. 1 (a), (b), and (c) show some typical 
examples of such operation on a Graflex shutter. Fig. 1 (a) was 
made with a rather low vertical-oscillator frequency in order to 
illustrate the principle. The horizontal distance represents the time 
during which a particular portion of the slit traversed the film. This 
time can be seen to vary from one end of the focal plane to the other, 




Fig. 1 (b) Same shutter with higher speed vertical sweep, showing change 
in speed of slit from top to bottom of focal plane. 

indicating that the shutter did not move at constant speed. Fig. 
1 (c) shows a properly adjusted shutter which moves at almost con- 
stant speed from one end of the image plane to the other. 

FLASHBULB TESTING 

Using almost exactly the same equipment, for example, an oscillo- 
graph and a phototube pickup, many other applications present 
themselves in photography. For example, the testing of photo- 
graphic flashbulbs and their light-output-versus-time characteristics, 
may be accomplished readily. A method, using the same basic 



68 BERKLEY AND FELDT July 

technique which was prescribed for shutters is now used as an Ameri- 
can Standard for testing photographic flash lamps. 10 It is also pos- 
sible to make recordings of the characteristics of a combustion type 
of flash lamp with a high-speed recording galvanometer. This equip- 
ment, however, fails when we attempt to measure the new gaseous- 
discharge microflash lamps, whose duration of light output may be of 
the order of a few microseconds; only a cathode-ray oscillograph can 




Fig. 1 (c) Same shutter properly adjusted for uniform slit travel. 

measure times of such order conveniently. Fig. 2 compares relative 
duration of shutter and flash. The circuit for studying these phenom- 
ena can be a very simple one. The gas tubes usually have an acces- 
sory ignition coil operated from a trigger circuit, consisting of a small, 
cold-cathode, gas tube. The same pulse which fires the cold-cathode 
tube can be used to start the sweep of the oscillograph. There is 
sufficient delay in the initiating tube so that the sweep starts before 
the ionization in the flash tube becomes appreciable. Fig. 3 show r s 
dual-beam oscillograms of such a photoflash tube in which a much 
higher shutter speed has been used, displaying the opening of the 



1949 C-R-TuBE APPLICATIONS 69 

shutter and the flashing of the lamp unsynchronized and synchro- 
nized. These are made with a shutter that shows considerable re- 
bouncing which, as mentioned previously, would not be indicated on 
an integrating type of shutter opening meter. The markers here 
are 25 microseconds apart instead of 1 millisecond. 

GLOSS MEASUREMENT 

One of the basic problems in optics is the proper description of the 
visual or optical character of a surface, the gloss of the surface. For 
this reason, in many industries so-called "standards" of various de- 
grees of gloss or surface finish are maintained. This problem is of 
importance in photography in connection with the proper specifica- 
tion of the surfaces on photographic papers. The so-called "feel" 




Fig. 2 Dual-beam recording of 
opening, plus electronic flashlight output. The time 
marking is given by a 40-kilocycle oscillator. 

of the surface, being a subjective matter, is of extreme importance 
in the final effect that a photograph produces upon the viewer. How- 
ever, no good method for specifying these surfaces, which assures uni- 
form quality and reproducibility, yet exists. For this reason, in 
every photographic supply store, there will be found so-called stand- 
ard samples of these various surfaces which serve as no specification 
whatsoever. 

The only satisfactory way, to date, of specifying the gloss of a sur- 
face is by drawing its complete reflectance curve as a function of the 
angle of view of the surface under certain standardized lighting con- 
ditions. This graph preferably should be plotted as a family of 
curves in order to express the effect throughout a solid angle. For 



70 BERKLEY AND FELDT July 

cases where the reflection is rotationally symmetrical about some 
point, a 2-dimensional curve such as the curve on a cathode-ray oscil- 
lograph, is sufficient and offers a very convenient means for obtaining 




(a) Synchronized. 




(b) Unsynchronized. 

Fig. 3 Dual-beam recordings of high-speed shutter and 
electronic flashlamp with high-speed sweep and 40-kilocycle 
(25-raicrosecond) time markings. 

these curves quickly. This can be done by many simple means. 
For example, this graph may be obtained in Cartesian co-ordinates 
merely by rotating the phototube around the sample illuminated in a 
standard fashion and expressing the output of the phototube on the 



1949 



C-R-TuBE APPLICATIONS 



71 



vertical plates, and by expressing its position by means of a potenti- 
ometer geared to the phototube on the horizontal axis. This type of 
presentation has been duplicated by slower methods, such as pen 
recorders. 

In some cases, however, it is desirable to do this very rapidly. For 
example, if we have a large number of samples, it is necessary, con- 
tinually, to draw these distribution curves. This may be done 
readily by means of the follow- 
ing system, which also enables- 
the use of a standard sample 
for comparison: two samples, 
one the standard and the other 
under test, are mounted back 
to back and spun by means of 
a synchronous motor about the 
axis of the motor. A phototube 
and light source are placed at 
some angle arbitrarily chosen, 
or at 90 degrees. As the 
samples are rotated by the 
motor, the angle at which the 
phototube alternately views 
the standard and the sample 
changes continuously. The 
phototube output displayed 
with a synchronous sweep on 
a cathode-ray tube is then a 
graph of light reflection as a 
function of the angle of view. 
Since the samples are pre- 
sented alternately, the curves 
appear simultaneous and superposed to the observer. 

Fig. 4 is a typical example of such a recording in which the reflection 
from a clear sheet of glass is compared with that of a sample treated 
with glare-reducing material. By means of intensity modulation, 
using a synchronized multivibrator, 3-degree angle markers have 
been put on the baseline which was recorded by double exposure. 
This technique, as mentioned previously, should find wide application 
in any industry where surface specification is desired. With this 
type of presentation, changes of reflectance characteristic during a 




Fig. 4 Relative reflection versus 
angle for clear glass (tall spike) and 
matte-coated glass. Angle markers 
on baseline are 3.6 degrees apart. 






72 



BERKLEY AND FELDT 



July 



drying process can be seen. This method may also be reversed by 
moving the phototube rapidly around the sample and drawing a great 
many curves as the sample dries. 

POLAR PRESENTATIONS 

It is more conventional in optics to express these light-distribution 
patterns in the form of polar rather than Cartesian co-ordinates. 
These patterns are generally used to describe the light distribution 
from lighting equipment such as photographic flood lamps. These 
patterns may be produced readily on cathode-ray oscillographs by 

simple means. Fig. 5 shows an 
instrument for this purpose, the 
Type 275 polar co-ordinate in- 
dicator. This instrument pro- 
duces polar diagrams which are 
synchronized with the motion 
of any rotating object merely 
by attaching a small lightweight, 
two-phase generator to the rotat- 
ing part. 11 If a phototube is 
placed on the rotating shaft its 
output can serve as a measure 
of the amount of light reaching 
a certain point from all angles 
by applying the output of the 
phototube to the radial-input 
Fig. 5-Polar co-ordinate oscillograph, terminal on this indicator. Simi- 
larly, the light source may be 

rotated and the phototube remain stationary. Fig. 6 (a) shows a 
Cartesian light distribution obtained from small flashlight bulb. 
Fig. 6 (b) shows a similar light-distribution pattern in polar co- 
ordinates on the Type 275-A indicator. Phototubes and cathode- 
ray oscillographs have also been used to scan the illumination 
of scenes being photographed to depict graphically the variation 
between high-light and shadow brightness so that, for example, 
the contrast range of the recording film is not exceeded. 12 

AUTOMATIC H AND D CURVE PLOTTING 

One of the best specifications for the behavior of a photographic 
emulsion is its H and D curve which relates the photographic density 




1949 



C-R-TuBE APPLICATIONS 



73 




(a) On Cartesian co-ordinates. 




(b) In polar co-ordinates. 
Fig. 6 Light distribution from small flashlight bulb. 

to the logarithm of the exposure. These curves are generally pro- 
duced by exposing either a stepped or continuously graded logarithmic 
variation of exposure along a strip of film, which is then processed in 
the usual manner. The dry film is examined by means of a densitom- 
iter and the results plotted on graph paper. This procedure is 
luite laborious and time-consuming. The shape of the H and D 



74 



BERKLEY AND FELDT 



Julv 



curve and its slope (the gamma) are affected widely by the conditions 
of development. 

In cases such as in motion picture processing where it is desirable 
to develop to constant gamma in the face of increasing exhaustion of 
the developer, sensitometric strips are frequently included every 
few hundred feet so that the development may be checked constantly, 
at least visually. This check would be much more useful if the actual 
curves were drawn as each strip passed through the developer so that 
the development could be shortened or prolonged as required. 

Such an H and D curve can be plotted easily by having the strips 
pass through an infrared light beam to a phototube while in the devel- 
oper. The resultant variation 
in density is displayed on a 
cathode-ray tube. 

We have produced such an 
H and D curve experimentally 
by examining the reflection from 
a sheet of paper exposed from 
an Eastman circular step wedge. 
The resultant H and D curves 
obtained at three different times 
during development are shown 
in Fig. 7. The exposed strip 
was mounted coaxially with a 
potentiometer, which produced 
horizontal positioning as the 
exposed sheet was rotated in a 
tray of developer. The wedge 
was illuminated by means of the vertical lamp which produced a small 
spot of nonactinic light on the paper. The reflection w r as plotted as 
a negative vertical deflection. The sharp peaks in the pattern are 
due to the black lines separating the various steps in the wedge. 

CATHODE-RAY-TUBE LIGHT SOURCES 

Present photographic flash lamps are gas-filled tubes and, therefore 
limited with respect to the shortest flash that they can produce, mostly 
because of the finite velocity of the gas particles. Since cathode- 
ray tubes are vacuum tubes, they are not subject to these limitations. 
By the use of phosphors having extremely short build-up and decay 
times, such as zinc oxide, it is possible to produce very short light 




Fig. 7 Three triple-exposed H 
and D curves. The bottom curve 
shows the start of development and 
the top curve the final appearance of 
the strip. 



1949 



C-R-TuBE APPLICATIONS 



75 



pulses. Several experimental cathode-ray tubes for use in producing 
these short light pulses have been built in connection with the 
relaying of video information over light beams. 13 In order to demon- 
strate the capabilities and advantages of such cathode-ray tubes over 
conventional lamps for stroboscopy at high speeds, the light-output- 
versus-time characteristics of such a cathode-ray tube have been 




Fig. 8 Double exposures comparing light from strobo- 
scope lamp with light from cathode-ray-tube light source. 




(a) (b) 

Fig. 9 Photographs of a wire rotating at high speed, 
made with (a) a stroboscope lamp, and (b) a cathode-ray- 
tube light source. The circle encloses the same wire in both 
cases. 

compared oscillographically with that of the light from a gas strobo- 
scope lamp. The results are shown in Figs. 8 and 9. Fig. 8 shows 
on the same time base, the oscillogram of a 2-microsecond flash from 
a cathode-ray tube (a small spike) and the comparatively long light 
output from a stroboscope. Not only is the stroboscope flash much 
longer in duration but it also rises and falls much less steeply and tends 
to oscillate. The effect of these light sources on a photograph is 
shown in Fig. 9. These two photographs are pictures of a wire being 



76 BERKLEY AND FELDT July 

rotated at high speed by means of a synchronous motor. The picture 
taken by means of the stroboscope is seen to correspond roughly to 
the oscillogram and to have both leading and trailing edges blurred 
while the photograph made with the cathode-ray-tube light source is 
acceptably sharp. Such cathode-ray tubes, capable of being modu- 
lated with high frequencies, also have been used successfully to replace 
the gas-crater glow modulator tube which is capable of modulation 
up to only about 15 kilocycles. These tubes have been successfully 
modulated at frequencies up to 10 megacycles. 

An oscillograph with a single-sweep beam-blanking circuit can be 
converted into a stroboscope of somewhat limited usefulness by the 




PSMOtiS! I* ' 

:s%*r 

^i 




Fig. 10 Negative and positive television motion pic- 
ture recording made with a continuous motion camera. 

use of a short-persistence cathode-ray tube. The length of each 
light pulse may be controlled by setting the sweep speed. For 
studying electrical or other machinery, it is frequently possible to 
obtain a synchronizing signal, connect it to the synchronizing signal 
input of the oscillograph, and have a workable stroboscope for illumi- 
nating small areas. A further advantage is the possibility of using 
the cathode-ray tube, both as a stroboscopic light source and as a 
viewing tube to study simultaneously the electrical and mechanical 
characteristics of some machine, or circuit. A further refinement lies 
in the use of a double-beam tube in which one beam acts as a strobo- 
scopic light source, the other beam as a conventional cathode-ray 
oscillograph. The advantage here is that very much higher speed 
phenomena may be studied than is presently possible with gas-tube 
stroboscopes. 



1949 



C-R-TuBE APPLICATIONS 



77 



By the use of such short decay and build-up phosphors, it is also 
possible to make continuous recordings of television programs from 
a cathode-ray monitor tube, for example, merely by using the film 
motion as the vertical sweep and allowing it to spread a complete 
record of each frame of the television picture along the length of the 
film. Fig. 10 shows two recordings made in this manner with a 
Type 314 oscillograph-record camera. There are here no complica- 
tions due to the differences in frame frequency and shutter frequency 
since no shutter is used on the camera. The same method is used in 
the present "Ultrafax" facsimile recording system. 

GEAR AND SPROCKET STUDIES 

One of the basic problems in the motion picture industry is that 
of obtaining accurate repeated sprocket teeth on motion picture 
camera and that of obtaining 
accurate repeated sprocket 
perforations on motion picture 
films and papers. 

If these perforations or 
sprocket teeth are not properly 
made, then the final theater 
image will weave up and down 
or from side to side or jump 
erratically, as anyone knows 
who has seen prints of old 
motion pictures. The accuracy 
and reproducibility of these 

perforations and sprocket ~ ptical setup for gear testing ' 

teeth may be studied easily by oscillographic methods. These 
methods involve a combination of optical and electronic magnifi- 
cation of the defects encountered. In order to display these 
defects on a cathode-ray oscillograph, a scanning technique is 
adopted in which the scanning element consists of a slit or small aper- 
ture placed in front of a phototube. The output of the phototube is 
then applied to the vertical plates of the oscillograph, after ampli- 
fication, if necessary. In testing sprocket teeth or the gears on mo- 
tion picture cameras, for example, the gear may be rotated at the oper- 
ating speed and the outline of the gear tooth picked up by means of 
the scanning slit. Fig. 11 shows the optical setup just described. 

If the sweep frequency on the oscillograph is equal to the time it 




78 BERKLEY AND FELDT July 

takes for one tooth to pass the slit then a repeated image of each 
tooth appears on the oscillograph screen. This image may have been 
enlarged optically before reaching the slit and may then be enlarged 
further by means of the vertical and horizontal amplifiers on the 
oscillograph. Any eccentricity in the gear tooth, either angular or 
radial, may readily be seen and amplified to the desired value. As 
shown in Fig. 12, this method has the advantage that it tests the 
gear under operating conditions so that the effects of dynamic un- 
balance or bearing eccentricity are apparent. A vibration pickup 




Fig. 12 Typical patterns obtained with perfect and de- 
fective gears. A perfect gear is shown in the upper left; an 
eccentric shaft in the upper right; and an irregular tooth 
size or angular spacing, below. 

may similarly be used in a conventional manner on the oscillograph 
to determine which of the gears in a motion picture camera is causing 
a repeated noise in the sound track, for example, by correlating the 
frequency of repetition of the pattern on the oscillograph with the 
rate at which various gears move in the camera. 

In the case of sprocket-perforation-accuracy measurements exactly 
the same technique is used, the scanning slit being similar to a sound- 
track slit. This technique of combined optical and electronic mag- 
nification will be illustrated by a very similar example, taken from 
another field, the testing of razor blades. Razor blades are manufac- 
tured in a continuous strip. The strips are sharpened on special 
grinding machines and are then honed and stropped. A microscope 



1949 



C-R-TuBE APPLICATIONS 



79 



and phototube have been used to look at the edge of each blade as it 
passes by. Fig. 13 shows the optical setup used. The sweep fre- 
quency on the oscillograph is synchronized with the repetition rate 
of the blades. The resultant patterns are shown in Fig. 14. The 
dips between patterns are due to the gaps between blades. The 
sensitivity here is equivalent to a magnification of 1000:1, about 100 
of this magnification being accomplished optically, the other factor 
of 10 accomplished electronically in the oscillograph amplifier so 
that a deflection of one inch on the cathode-ray-tube screen is equiva- 
lent to Viooo inch on the razor blade. The pictures show a number of 



BLADE STRIP, 




Fig. 13 Optical setup for razor-blade testing. 

blades which are perfect and some blades which have nicks about 
1 /2oooth of an inch deep. 

AUTOMATIC PRINTER ADJUSTMENT 

One of the basic problems in the photofmishing industry is to 
obtain a properly exposed and developed set of prints from a widely 
varying series of negatives. This is usually accomplished by a hit- 
or-miss system which is based solely upon the judgment of the 
printer in the darkroom. This precludes accurate duplication of 
results from one photofinisher to another. Some attempts have been 
made to use electronic exposure controls which automatically adjust 
at least the exposure for these widely varying negatives. The dark- 
room operator still has to select the proper grade of printing paper. 

A suggested approach to this problem is to print each negative to 



80 BERKLEY AND FELDT July 

suit the personal preferences of the customer instead of attempting to 
make- all pictures of uniform quality. These personal desires with 
respect to the artistic effect of the print may be determined by means 
of electronic equipment, operating as follows: 

This machine, to be placed in the photofinisher's anteroom, consists 
of a simplified television imaging system such as a flying-spot scanner. 
When the negative is placed in the machine, a positive image appears 
on the cathode-ray-tube screen which shows how the final print will 
look. There may be only two adjustable controls on this machine, 
one controlling the gamma of the image and calibrated directly in 
contrast grade of the printing paper. The second control is a bright- 




Fig. 14 Pattern obtained with razor-blade tester, show- 
ing a number of defective blades, compared with the edges 
of good blades. 

ness control calibrated directly in exposure time required for the 
selected brightness. After adjusting the controls until a picture hav- 
ing the proper aesthetic effect is obtained, the print can be made under 
well-defined reproducible conditions. 

Another and more serious problem exists in color-film printing. It 
is very difficult to make a good color print from a color negative with- 
out a trial-and-error process. Much of the guesswork can be taken 
out of this process by applying the above principles to it. Various 
methods have been proposed in the patent literature to enable an 
electronic viewing of a negative and a suitable phase and color reversal 
so that the appearance of a positive may be directly determined and 
the proper corrective measures taken. 



1949 



C-R-TuBE APPLICATIONS 



81 






SOUND RECORDING 

Since the earliest days of the cathode-ray tube, various types of 
tubes have been proposed for use as sound-recording elements in 
sound-on-film systems. One of the first to suggest this use and to 
build cathode-ray tubes for this purpose was von Ardenne, 14 who 
built the equipment and actually made such recordings. It is possi- 
ble to make such sound recordings with perfectly standard cathode- 
ray oscillograph equipment and a continuous recording camera such 
as the Type 314 camera. Fig. 15 shows some examples of such sound 




Fig. 15 Typical cathode-ray-tube sound-track recordings. 

recordings made by voice-modulating a 100-kilocycle signal in a 
mixer tube and recording the result with the camera. These signals 
may be played back readily on the oscillograph by scanning them 
with an illuminated slit in a conventional manner. The advantage 
of the cathode-ray oscillograph here is that there is no limitation as to 
frequency response in the recording element itself, since modulating 
frequencies as high as desired may be recorded and played back. 
Obviously, a cathode-ray oscillograph is the best tool for properly 
studying, adjusting, and describing the performance of electronic 
motion picture sound equipment. Such phenomena as hum, cross 
modulation, and intermodulation may be recorded readily by stand- 
ard techniques and many references appear in the literature 'to these 
methods. 






82 



BERKLEY AND FELDT 



July 




(a) Showing incandescence. 




(b) Showing nigrescence. 

Fig. 16 Ripple in small alternating-current-operated 
lamps. These recordings made with repeated sweep. 

STUDY OF LIGHT SOURCES FOR RIPPLE 

One of the difficulties in illuminating a motion picture set with 
tungsten lamps is that the power supply must in many cases, be direct 
current in order to avoid a brightness flicker in the final image due to 
the 120-cycle variation in the light emitted from alternating-current- 
operated lamps. This variation causes an annoying beating of the 
frame frequencies with the ripple frequency and if a camera is to be 
operated at high speed, this flicker may become very annoying. Par- 
ticular difficulty is encountered in cases where a motion picture has 
been made at high speed of a phenomenon illuminated by alternating- 



1949 C-R-TuBE APPLICATIONS 83 

current-operated lamps and then the film printed on a high-speed 
printer also operated on alternating current. Occasionally, the dips 
in the exposing-light output and printing-light output become syn- 
chronous, with resulting light fluctuation in the final projected image. 
In recent years, many new types of filament construction have been 
adopted to minimize this defect and to produce as little ripple as 
possible. The best way to study this ripple is on a cathode-ray oscil- 
lograph equipped with a direct-current amplifier so that the ripple 
may be expressed as a percentage of the total light output. Fig. 
16 (a) and (b) illustrates some typical examples of the ripple per- 




Fig. 17 Spectrograms of a low-pressure mercury arc at 
various times in seconds after starting. 

centage of a certain lamp. In making these oscillograms, it was also 
of interest to determine which of these lamps lent themselves most 
readily to modulation for. the transmission of information over light 
beams. The incandescence and nigrescence* curves can easily be seen 
and studied on these cathode-ray oscillograms. 

COLOR SPECIFICATION 

Another problem in photography and optics is the proper de- 
scription and specification of various colors. A cathode-ray-tube 
spectrograph for accomplishing this very result has been described by 

1 "Nigrescence" is denned as the process of becoming dark and refers here to the 
exact manner in which the light output of a lamp decreases after the current 
is suddenly cut off. 



84 BERKLEY AND FELDT July 

the authors. 15 - 16 Fig. 17 shows some typical cathode-ray-tube- 
produced spectrograms made with this apparatus. This instrument 
produces the color information required within 1 / 130 second. The 
information may readily be put into other standard forms such as 
into International Commission on Illumination co-ordinates. To 
obtain the ICI co-ordinates requires certain standard integrations, 
additions, and divisions which may be accomplished electronically, by 
converting the information into digital form. To indicate these ICI 
co-ordinates, a cathode-ray tube again is a useful tool since a Uni- 




Fig. 18 Light distribution in image showing chro- 
matic aberration. Pattern at left, at center of image; at 
right, at edge of image. 

versal ICI color diagram may be placed over the face of the tube, the 
position of the spot enabling reading of the co-ordinates directly. 
The output of a 3-filter photometer may also be shown in this manner 
instantaneously on the cathode-ray-tube screen. 

Another use of the cathode-ray tube spectrograph in optics is in 
the study of the color aberrations of optical systems. Fig. 18 shows 
the color distribution of the image of a rather poor lens along the 
axis, and the color at one of the fringes of the image. Many other 
uses for this instrument have already been described, such as the 
immediate drawing of filter-transmission curves or the reaction 
between chemical solutions, indicating, for example, when a developer 
has reached the exhaustion stage. 



1949 C-R-TuBE APPLICATIONS 85 

CONCLUSION 

While it has not been possible to give here a complete description 
of all cathode-ray tube applications considered in optics and photog- 
raphy, it should now be obvious that cathode-ray tubes and oscillo- 
graphs are valuable tools for solving many technical problems. 
Because of lack of space, we have not been able to consider many of 
these in the detail they deserve or to include many which have been 
developed outside of our Laboratories. 

It is hoped that this brief consideration of some applications will 
stimulate the use of these oscillographic techniques in as wide a 
range of problems as possible. 

REFERENCES 

(1) C. B. Neblett, "Photography," D. Van Nostrand, New York, N. Y., pp. 
152-153, 1927. 

(2) T. H. Bullock, "Testing shutters with the cathode-ray oscillograph," 
Amer. Photog., vol. 38, pp. 24-27; September, 1944. 

(3) Van Liempt and DeVriend, "Testing focal plane shutters with the help of 
the cathode-ray oscillograph," Physica, pp. 811-827; October, 1937. 

(4) American Standards Association, "Method of Determining Performance 
Characteristics of between-the-Lens Shutters Used in Still Picture Cameras," 
Z52.63-1946, Approved January 18, 1946. 

(5) American Standards Association, "Method of Determining Performance 
Characteristics of Focal Plane Shutters Used in Still Cameras," Z52.65-1946, 
Approved January 24, 1946. 

(6) D. T. R. Dighton and H. McGross, Jr., "Cathode-ray tube shutter-testing 
instrument," /. Sci. Instr., vol. 24, pp. 128-133; May, 1947. 

(7) R. F. Redemake, "Electronic shutter- testers," Electronics, vol. 11, pp. 
26-27; January ,'1938. 

(8) D. T. R. Dighton, "An electronic shutter tester," Electronic Eng., (Eng- 
land), vol. 20, p. 251; August, 1948. 

(9) L. Kalman, "A new method of testing photographic shutters," Schweizer 
Archiv., vol. 11, pp. 175-181; 1945. 

(10) American Standards Association, "Lamps; Photographic, Flash," Z52.43- 
1944-W-L-122, February 2, 1945. 

(11) M. Maron and M. B. Kline, "The DuMont Type 275-A cathode-ray polar- 
coordinate indicator," The Oscillographer, vol. 9, pp. 1-3; September-October, 
1947. 

(12) E. R. Thomas, "A portable brightness distribution photometer," /. Sci. 
Instr., vol. 23, p. 187; August, 1946. 

(13) "Television on modulated light beam," Tele Tech., vol. 6, pp. 96-97; 
January, 1947. 

(14) M. vonArdenne, "Cathode-ray tubes," Sir Isaac Pitman and Sons, Lon- 
don, England, 1939, pp. 462-473. 

(15) R. Feldt and C. Berkley, "The cathode-ray spectrograph," Proc. Nat. Elec. 
Con/., pp. 198-211; October, 1946. 

(16) "Infrared spectrometer," Electronic Eng. (England), vol. 20, p. 331; Octo- 
ber^ 1948. 



Objective Lenses of //I Aperture 
and Greater* 



BY EDWARD K. KAPRELIAN 

SIGNAL CORPS ENGINEERING LABORATORIES, FORT MONMOUTH, 
NEW JERSEY 

Summary The factors involved in the design of large-aperture objectives 
are discussed and some of the general approaches to the reduction of the 
various aberrations are presented. Diagrams, classification, and source 
references of most objectives of //I aperture or greater which have been 
published are included. Both refracting and reflecting systems are consid- 
ered, including objectives having spherical and aspherical surfaces and those 
employing the immersion principle. Applications, testing, and performance 
of extreme-aperture objectives are discussed. An extensive bibliography is 
appended. 

INTRODUCTION 

DURING THE PAST SIXTY YEARS the relative aperture of a well- 
corrected objective for normal field of view has been increased from 
about //5 to about //1.4, some twelve times. The brightnesses of the 
carbon arc and the incandescent electric lamp have increased about 
six times and thirty times, respectively, in the same period, and new 
sources of great brightness such as the high-pressure mercury arc, the 
mercury-cadmium arc, and the condenser discharge flashtube have 
been developed. The sensitivity of the fastest film of today is more 
than fifty times that of the most rapid plate of the 1890 ; s. As a result 
of these advances the lens-light source combination and the lens-film 
combination can be several hundred times more effective than they 
were when perforated film was first employed in cinematography. 
Film speeds and light-source brightnesses can continue to increase; 
with effective lens speeds the ultimate, while not attained, is at least 
clearly defined. 

ILLUMINATION OF THE IMAGE 

The maximum light-gathering power of an aberrationless lens 
system is limited and in the case of a dry lens, i.e., one having both 
object and image in air, the greatest possible "speed" is//0.5. Fig. 1 

* Presented April 8, 1949, at the SMPE Convention in New York. 
86 JULY, 1949 JOURNAL OF THE SMPE VOLUME 53 



OBJECTIVE LENSES 87 

shows in cross-section portions of a fanciful objective having an aper- 
ture which approaches this maximum. The //2 ray strikes the axis 
at the image plane at an angle of 14V 2 degrees; the //I, //0. 7, and 
//0.53 rays strike the axis at angles of 30, 45, and 70V2 degrees, re- 
spectively. An//0.5 ray would strike the axis at the limiting angle of 
90 degrees, just grazing the image plane. The illumination E in foot- 
candles at the axis of an aberrationless image is 

k (^'Y TT 3 sin 2 0, (1) 

where k is the light-transmission factor of the lens, n' and n are the 
indexes of refraction in the image and object spaces, respectively, B is 
the brightness of the object in candles per square foot, and B is the 
angle between the axis and the extreme, or marginal, ray reaching the 
image. An exceptionally lucid presentation of lens speed and of the 
factors involved is to be found in a paper by Kingslake. 1 

IMAGE DEFECTS' AND APERTURE 

As the semidiameter of the lens increases to approach the value of 
focal length as the limit, the rays passing through the outer zones are 
acted upon more and more violently by the refracting surfaces. Of 
the various unfortunate effects these refractions have upon the image, 
spherical aberration will be considered first. In a given system of 
large aperture it will be found that at any strongly curved surface, 
other than one which is aplanatic or zero-refracting, angular refraction 
will increase very rapidly with the height of the ray. The rays near 
the axis will be refracted an amount substantially proportional to 
their angle of incidence while the//l,//0.7, and //0. 53 rays will strike 
the refracting surface at greater angles of incidence with the con- 
sequence that the differences between the angles of incidence and the 
angles of refraction will increase disproportionately somewhat in the 
manner shown at surface 3 of Fig. 1. Consequently, the rays in the 
outer zones will intersect the axis at points displaced from the inter- 
section point of rays in the more central zones unless corrected by 
refractions producing an equal effect of opposite sign. Spherical ab- 
erration reduces contrast and resolving power more or less severely de- 
pending upon the distance between the intersection points of rays being 
refracted by the various zones and upon their manner of distribution. 

Reduction or elimination of this undesirable behavior of the light 



88 



KAPRELIAN 



July 



rays may be accomplished in part by utilizing shallower curves, em- 
ploying aplanatic and zero-refracting surfaces, increasing the indexes 
of refraction of the glasses, and by "bending" changing the shape 
factor of an element without altering its power. The necessity for 
employing shallower curves logically suggests the use of more ele- 
ments, and the practice of substituting for a single element two others, 
each having half the power of the single element, can reduce the 
spherical aberration by 3 /4- Application of these principles in de- 
signing objectives of large aperture will usually reduce spherical 
aberration to an acceptable level. 

Axial, or longitudinal, chromatic aberration may also be reduced to 
a level where it is not objectionable in view of the large variety of 
glasses available to the designer; for a given refractive index there are 



V PRINCIPAL PLANE 




Fig. 1 Refraction at large apertures. 

usually several, and occasionally a half-dozen glasses of different dis- 
persion. Lateral chromatic aberration does not present too great an 
obstacle to the design of extreme-aperture objectives and can be re- 
duced to a point where it is far less objectionable than, for example, 
astigmatism and curvature of field. Usually slight changes of spacing 
are sufficient to balance the v numbers* and spacing and powers of the 
elements before and behind the stop. 

Distortion, resulting in variation in magnification across the image 
surface, is corrected in a manner not unlike that employed in correct- 
ing lateral chromatic aberration; that is, by balancing powers and 
separations on each side of the stop. 

The remaining aberrations, i.e., coma, astigmatism, and curvature of 
field, are severely aggravated by the conditions accompanying large 

* The v number of a glass is the reciprocal of the dispersive power; it is equal to 
the index for the sodium D line minus one, divided by the index difference for the 
hydrogen F and C lines. 



1949 OBJECTIVE LENSES 89 

relative aperture and require other treatments for their correction, and 
it is the difficulty of reducing these extra-axial aberrations v^hich has 
generally led to the lens types and modifications to be discussed be- 
low. For example, the reduction of coma is most expeditiously ef- 
fected by designing for approximate symmetry about the stop; this 
accounts for the presence among extreme-aperture objectives of those 
of the Gauss type. Reduction of astigmatism and curvature of field 
requires a low Petzval sum which can be accomplished by introducing 
appreciable air spaces among the components, by utilizing high- 
index, high-v crowns, and by adding a negative lens (field fiattener) 
close to the image plane. Since all of these bendings, spaciiigs, choices 
of indexes and dispersions, and distributions of power cannot be 
effected simultaneously because one action precludes or is only 
partially compatible with another, every design is a compromise of 
aberrations favoring the intended application of the objective, with 
the concessions as little damaging as the skill of the computer and the 
budget of the latter's employer permit. 

The refinement of photographic objectives has been gradual and 
steady, principally through the small contributions of many workers 
and only occasionally through a new concept. The recent history and 
development of the photographic objective has been recorded and 
classified in papers by Taylor and Lee, 2 Lee, 3 and Kingslake 1 ' 4 and in 
texts by Merte 5 and Leistner. 6 - 7 A consolidation here of the results 
of these efforts as they pertain to extreme-aperture objectives shows 
to what extent the limit has been approached, by what means and 
with what results. The only designs to be considered comprise those 
objectives of //I aperture or greater, including refractors and re- 
flectors utilizing either spherical or aspherical surfaces, for which 
data are obtainable in the literature, or which have actually been 
issued. The selection of //I as the smallest aperture to be considered 
is arbitrary; designs of //1. 3 to //1. 5 aperture exist which may be 
quite capable of being produced in apertures of //I or faster. 

REFRACTING OBJECTIVES SPHERICAL SURFACES 
A substantial number of large-aperture refracting objectives follow 
the Petzval design, outstanding for its excellent correction over a 
small field. In its fundamental form the Petzval lens is essentially a 
pair of widely spaced achromats, each approximately corrected for 
spherical aberration. The earliest of these modifications is the Ziess 
R-Biotar//0.85, Fig. 2a, computed by Merte 8 which in the 4. 5-centi- 
meter focal length covers most of the 16-rnm frame reasonably well. 



90 



KAPRELIAN 



July 


















In this design the creation of an air space between elements 1 and 2 of 
the original Petzval lens and provision of another collective element 
(3) have provided the necessary additional degrees of freedom. An- 
other design, Fig. 2b, of aperture //0.9, has been developed by War- 
misham, 9 in which the large aperture is obtained by the addition of a 






1949 OBJECTIVE LENSES 91 

collective meniscus immediately following the first doublet, a pro- 
cedure favorable to the reduction of spherical aberration. Fig. 2c 
shows the Taylor, Taylor, and Hobson //0.8 radiographic lens, 10 a 
design in which the rear component of the basic Petzval configuration 
is split into two doublets, again taking advantage of reduced spherical 
aberration through dividing. The//0.6 lens of Kaprelian, 11 Fig. 2d, 
adds another element to the R-Biotar upon which it is based in an 
attempt to obtain better spherical and chromatic correction and to 
increase the back focal length by a shift in power. 

Another group of large-aperture objectives is based upon the ex- 
cellent six-piece Gauss type, the principal defects of which are higher 
order astigmatism and oblique spherical aberration. Leitz, 12 Fig. 2e, 
has utilized a modification of the Gauss type which comprises the ad- 
dition of two crown elements, one before the dispersing menisci and 
one after the menisci, to*extend the aperture to //0.85. The 7. 5-centi- 
meter Leitz objective has an acceptable field of about one inch diam- 
eter and covers the 35-mm frame for cine fluorography. An //I 
lens produced by Wray for radiography is of the same general type ; 
here the additional collective element has been provided only at the 
long conjugate end and the second dispersive element appears as a 
singlet. The Wray lens, in common with most objectives intended for 
radiography, is especially corrected for use at short conjugates, 

An //0.95 Gauss-type objective of Zeiss 13 provides additional 
power through the provision of a second rear crown and includes a 
field flattener close to the focal plane, Fig. 2f. Herzberger 14 has de- 
signed an objective, Fig. 2g, of //0.8 aperture which utilizes a front 
group comprising a complete, well-corrected Gauss objective followed 
by a rear-collective group of three elements based upon a system 
originated by Luboshez. 15 - 16 The Herzberger objective provides for 
generally good correction. The Astro Tachon //I of Bielicke 17 
utilizes the front components of the Gauss type in combination with 
rear components derived from the air-space type. Bielicke's //I de- 
sign has been modified by the addition of another element to produce 
the;/0.95 Tachon, Fig. 2h. 

Another group of extreme-aperture objectives derives from the 
Gauss type to form a separate and distinct class which results when 
the second dispersive meniscus is removed, the last element made 
strongly collective, and a meniscus introduced between the front ele- 
ment and the dispersive meniscus. Lee, 18 Fig. 2i, achieves an aper- 
ture of //I by this approach and in another form, Fig. 2j, also of //I 






92 KAPRELIAN July 

aperture, the rear element is split in two without altering the first 
six radii or changing glasses. Lee 19 has also produced an f/l design, 
Fig. 2k, in which the front element of this general arrangement is 
replaced with a cemented doublet to provide additional surfaces. 
Closely following this latter arrangement, Fig. 21, is the f/l Taylor 
and Hobson 10 radiographic lens in which an air space has been in- 
troduced between the first two elements. 

Other lenses not directly identified with the above type groupings 
include an //I modification of the Ernostar by Bertele, 20 Fig. 2m, in 
which the rear crown has been replaced by a pair of crowns; a varia- 
tion of the Plasmat by Rudolph, 21 Fig. 2n, for which an aperture of 
f/l is claimed; and two f/l designs, Figs. 2o and 2p, by War- 
misham, 22 ' 23 the first of which is derived from the four-piece air-space 
Dogmar design while the second is a modification of the Speed Pan- 
chro. Hopkins, Evans, Covell, and Feder 24 haVe described a six-piece 
f/l objective based upon a microscope objective, or Petzval, design 
in which the well-corrected image falls upon a curved field to which 
the film is deformed pneumatically. 

Of historic interest is an early and unusual design of Minor 25 for 
which an aperture of //0.5 is claimed. Minor's design began with the 
computation of a four-piece air-space objective providing for the 
addition, later, of three more elements, one in front and two behind the 
basic objective to obtain increased aperture with the apparent utiliza- 
tion of specific surfaces to correct for specific aberrations. The final 
large aperture claimed was to be obtained by adding to the existing 
system a pair of rear elements which was intended to constitute a 
large-aperture rear attachment. 

Of these twenty designs, six are currently, or have at some time 
been commercially available. Another, a Petzval lens, nominally of 
//0.99 aperture, has not been considered here because its actual 
effective aperture is about//! .4. Objectives which do not appear even 
approximately to fulfill the sine condition, such as one dry objective 
of //0.3 aperture, 26 have been omitted from the present paper. Other 
large-aperture objectives having only partial corrections 27 or intended 
for nonphotographic uses, 28 may be of interest in some applications. 

REFRACTING OBJECTIVES ASPHERICAL SURFACES 

The use of aspheric surfaces in large-aperture refracting objectives 

permits substantial reduction of spherical aberration and coma while 

maintaining an economy of the number of elements employed or 

allowing the other elements to be applied to the correction of other 



1949 



OBJECTIVE LENSES 



93 



aberrations. At present, aspheric surfaces of glass having the ac- 
curacy necessary for use in photographic objectives cannot be mass- 
produced; the high cost of hand-figuring and the difficulty of testing 
during manufacture have prevented extreme-aperture photographic 
objectives with aspheric surfaces from appearing commercially. The 
probability that methods and techniques for the production of such 
surfaces on a large scale may be developed in the near future, possibly 
through the use of materials other than glass, warrants the design and 
study of these objectives. 

Lee 29 has shown, Fig. 3a, an //I design similar to that of Fig. 2i in 
which concave surface 7 is aspheric, changing from a sphere at its 
central zones to a conicoid at the outer zones. Djian 30 discloses 




GRAY f/0.7 
Fig. 3 Refracting objectives having aspherical surfaces. 

several modifications of much the same type, one of which, Fig. 3b, 
attains the aperture of //0.57. Djian aspherizes a convex surface (3) 
by constructing the second element of four pieces of the same type 
of glass cemented together, each succeeding piece in the light path 
extending beyond the previous piece and presenting aspherical front 
surfaces of increasing radius to the rays in the outer zones. 

Another approach is that of Gray, 31 Fig. 3c, in providing an objec- 
tive with an aspheric correcting plate at the long conjugate end to 
provide a 1-inch //I objective of //0.7 aperture which is capable of 
satisfactorily covering 16-mm frame size. 

REFLECTING OBJECTIVES 

Reflecting systems offer a variety of advantages for large-aperture 
applications which are bound to tempt the computer. By comparison 
with a refractor of the same power, the spherical reflector has a longer 






94 



KAPRELIAN 



July 



radius, it can have a more favorable Petzval sum, and it has a small 
fraction of the spherical aberration. There is a complete absence of 
chromatic aberration in the front-surface reflector and by placing the 
entrance pupil at the center of curvature of a spherical reflector, 
coma, astigmatism, and distortion can be reduced to zero. Reduction 
of spherical' aberration and appropriate flattening of the field are the 
principal goals in the utilization of mirrors as photographic objectives. 
The first large-aperture reflecting system of extended field is that 
accredited to Schmidt, 32 - 33 Fig. 4a, which utilizes a spherical reflector 
and an aspheric corrector plate. It is generally well corrected except 





SCHMIDT P/0.7 



SONNEFELD f/0.5 





HOUGHTON f/0.6 BOUWERS f/0.9 

Fig. 4 Reflecting objectives. 

for curvature of field. The Schmidt system has had numerous applica- 
tions and has been modified in a variety of ways even though the image 
falls inconveniently between the mirror and the correcting plate and 
though the latter is not readily or inexpensively produced at present. 
A logical next step was the elimination of the aspheric correcting 
plate. This was done by Sonnefeld, 34 Fig. 4b, who utilized a dis- 
persing corrector comprising a positive and a negative element having 
spherical surfaces to correct the image formed by a Mangin mirror 
rather than by an ordinary front-surface spherical mirror to achieve 
an aperture of //O.5. Mangin-mirror arrangements of //0.9 and 
//0.6 apertures are described by Flugge, 36 and Martin, Flugge, and 
Roll 36 have utilized a Mangin mirror hi combination with refracting 
elements to produce a system of //0.8 for television projection with- 
out the use of aspheric surfaces. Houghton 37 obtains an aperture of 



1949 OBJECTIVE LENSES 95 

f/0.6 by combining a dispersive air-spaced triplet with a front-sur- 
face spherical reflector, Fig. 4c. 

Use of a substantially zero-power concentric meniscus lens, which is 
also concentric to the mirror which it corrects, has been made by 
Maksutov 38 and by Bouwers, 39 ' 40 Fig. 4d, to obtain large fields with 
large apertures, the aperture being limited only by zonal aberrations 
and longitudinal chromatic aberration. For those applications re- 
quiring extreme aperture where curvature of field to a radius approxi- 
mately equal to the focal length is not objectionable, systems of this 
type may be preferable to straight refracting objectives in the present 
state of the art. The simplicity of concentric systems from the view- 
point of both construction and computation, axial tracing and design 
suffice for the entire field of view, makes these objectives attractive. 
Application of this principle to television projection has been made by 
Bennett 41 who has obtained an aperture of //O.8. Bouwers 42 has 
further improved the corrections obtainable with the concentric 
system by providing an aspherical correcting plate in an arrangement 
in which the mirror is corrected by a substantially concentric double 
meniscus. Baker 43 has utilized as the correcting means in one modi- 
fication of the concentric system of //0.6 aperture a pair of menisci with 
their concave surfaces facing an aspheric correcting plate of very weak 
curvature. A similar approach, but without a corrective plate, has 
been presented by Wynne. 44 Gabor 45 has disclosed a reflecting system 
of //0.9 aperture based upon the same general principles as that of 
Maksutov and Bouwers. In Gabor a secondary mirror permits the 
more convenient positioning of the image just at the rear of the pri- 
mary mirror. Henyey and Greenstein 46 have described a concentric 
system of about //I aperture for photofluorography which utilizes an 
achromatized correcting meniscus. In another report 47 by these in- 
vestigators, additional systems of various configurations are shown. 

The parabolic mirror is ideal for telescope imagery but suffers so 
badly from coma that it cannot be employed for photography where 
both large aperture and extended field are requisite. Warmisham 48 ~ 63 
has succeeded in combining spherical and aspherical mirrors with and 
without aspheric correcting plates to produce a family of large-aper- 
ture objectives, some of which are suitable for photography. 

It should be noted that in each of these mirror systems there is 
vignetting either from the photographic film or from a secondary 
mirror which has the effect of blocking the light from the central zones 
responsible for much of the sharpness in a lens. The rays from the 



96 KAPBELIAN July 

outer zones which contribute most of the aberration in any system 
form the image in these systems and must therefore be highly cor- 
rected. Because of the location of the image between the corrector 
and mirror, many of these objectives do not lend themselves to ready 
utilization as taking lenses caused by shutter problems, nor are they 
adapted for use in ordinary projection systems. 
IMMERSION OBJECTIVES 

The brightness of an image depends upon the ratio of indexes of re- 
fraction in the image and object spaces as well as upon the angle of the 
extreme ray (equation (1)). Thus the use of an immersion fluid of 
index 1.5 between the focal plane and the rear element of an immer- 
sion objective more than doubles the "speed" of the lens. It is thereby 
possible to obtain relative apertures of //0.4 or slightly faster with the 
accompanying advantages or disadvantages of increased theoretical 
resolving power and reduced depth of focus. 

The difficulties and inconveniences associated with the immersion 
principle limit its use to very few applications. Bracey 54 employed an 
enlarged oil-immersion microscope objective of //0.36 aperture for 
astronomical photography. One form of the Djian 30 objective not 
dissimilar to that shown in Fig. 3b, is especially adapted for immersion 
use and attains an aperture of //0.54 through oiling the film to the 
rear plane surface of the system. A variety of high-speed Schmidts, 
including solid modifications, have been described by Hendrix and 
Christie 55 and an aperture of //0.3 has been attained by Baker 56 
utilizing a solid system. Nicoll 57 has shown an immersion Schmidt 
system of large aperture applied to picture taking and to television 
projection. Solid Schmidts and solid concentric systems of approxi- 
mately//! aperture or greater are to be found in Henyey and Green- 
stein. 47 In those applications where the ultimate in light-gathering 
power is essential and the inconveniences of the immersion systems 
are secondary considerations, these systems represent the only purely 
optical means whereby this extreme lens speed may be attained. 

APPLICATIONS 

There are a number of reasons to account for the fact that very few 
extreme-aperture objectives are available commercially: they re- 
quire extensive design time, are costly in view of the complexity of 
construction and the limited production for a specialized market, and 
the performance at present of all-refracting objectives having spheri- 
cal surfaces only is at best mediocre in comparison with well-designed 
objectives of //1. 5 or//2 aperture. An//0.85 objective may resolve 15 



1949 OBJECTIVE LENSES 97 

to 20 lines per millimeter on the axis and only 5 to 8 lines per millimeter 
at the corner of the 16-mm frame while at least one recent mass- 
produced//!^ lens can resolve 60 lines per millimeter and 45 lines per 
millimeter at the center and edge, respectively, of the same field on 
the same high-speed emulsion. Extreme lens speeds are valuable in 
those applications where object brightness is low as in cine fluorog- 
raphy, where exposures are extremely short as in ultrahigh-speed 
photography, and in those situations where short exposure times are 
necessary at locations of low light level where the use of lamps is ob- 
jectionable. They may also be useful in projection where excep- 
tionally high levels of screen illumination must be obtained or where a 
given high screen illumination must be maintained with an economy 
of light-source power or with light sources of relatively low brightness. 

An optical disadvantage of these extreme-aperture objectives, 
aside from lack of high resolution, is the extremely shallow depth of 
focus. In order to realize the full resolving power of an //0.8 objective 
capable of separating 40 lines per millimete-r the emulsion must be 
positioned within 0.016 mm (0.0006 inch) of the image plane. Clearly 
the taking or projecting equipment intended for use with an objective 
of such aperture must be properly designed and fabricated. It is also 
important to recognize the low light-transmission factor in refracting 
objectives, where, notwithstanding the use of low reflection coatings, 
there still will be considerable light loss at the 10 or 12 glass-air sur- 
faces in addition to significant loss due to long glass paths. For those 
applications where a considerable amount of the light is at the violet 
end of the spectrum there may be a disproportionately large loss due 
to the use of extremely dense flint elements in the design. 

Testing of extreme-aperture taking lenses is best performed by 
photographic means, preferably utilizing the subject contrast and 
type of emulsion with which the objective is to be employed. Visual 
tests on an optical bench are convenient, although* evaluation is 
difficult because of the high magnifications which accompany the use 
of large numerical-aperture microscope objectives and partly because 
the observation is subjective. It is essential that the numerical aper- 
ture of the microscope objective used on the optical bench be at least 
as great as that of the objective under test. In testing an objective 
of //I, //0. 85, or//0.6 aperture, the numerical aperture of the micro- 
scope objective must be not less than 0.5, 0.59, or 0.83, respectively, 
otherwise the observed image will be that formed by the objective 
when stopped down to the aperture corresponding to the numerical 



98 KAPRELIAN July 

aperture of the microscope objective. Projection means utilizing a 
projection test slide may also be employed for testing these objectives, 
provided the projector condenser is of an aperture capable of filling 
the objective with light. 

For those photographic applications where even the great light- 
gathering power of an extreme-aperture objective is insufficient or 
where the speed of such an objective must be maintained while en- 
joying the greater depth of focus, higher contrast and higher resolving 
power of an objective of more modest aperture, an electronic stage 
such as an image tube or an image orthicon, or other intermediate 
means such as phosphors, provide the next obvious step for increasing 
the amount of energy in the image. 

REFERENCES 

(1) R. Kingslake, "The design of wide aperture photographic objectives," 
/. Appl Phys., vol. 11, pp. 56-69; January, 1940. 

(2) W. Taylor and H. W. Lee, "The development of the photographic objec- 
tive, Proc. Phys. Soc. (London), vol. 47, pp. 502-519; January, 1935. 

(3) H. W. Lee, "New lens systems," Phys. Soc. (London), Reports on Prog- 
ress in Physics, vol. 1, pp. 130-149; 1940. 

(4) R. Kingslake, "Optical glass from the viewpoint of the lens designer," 
J. Amer. Ceramic Soc., vol. 27, 189-195; June, 1944. 

(5) W. Merte, "Das Photographische Objektiv Seit dem Jahre 1929," Ergan- 
zungswerk I, Handbuch der Wissenschaftlichen und Angewandten Photographic, 
vol. 1, pp. 1-98, Springer, Berlin, 1943. 

(6) K. Leistner, "Photographische Optik," Fortschritte der Photographic 
II, Akademische Verlagsgesellschaft, Leipzig, 1940, pp. 27-73. 

(7) K. Leistner, "Photographische Optik," Fortschritte der Photographic III, 
Akademische Verlagsgesellschaft, Leipzig, 1949, pp. 291-302. 

(8) W. Merte, U. S. Patent 1,967,836 (1934). 

(9) A. Warmisham, British Patent 485,096 (1938). 

(10) A. Cox and H. W. Martin, "The assessment of lenses," J. Sci. Instr., 
vol. 22, pp. 5-12; January, 1945. 

(11) E. Kaprelian, U. S. Patent 2,424,827 (1947). 

(12) E. Leitz, Deutsches Reich Gebrauchmuster, 1,285,900 (German petty 
patent, about 1932). 

(13) C. Zeiss, French Patent 884,478 (1943). 

(14) M. Herzberger, U. S. Patent 2,186,605 (1940). 

(15) B. E. Luboshez, U. S. Patent 1,910,115 (1933). 

(16) B. E. Luboshez, U. S. Patent 1,952,268 (1934). 

(17) W. Bielicke, U. S. Patent 1,839,011 (1931). 

(18) H. W. Lee, U. S. Patent 2,012,822 (1935). 

(19) H. W. Lee, British Patent 419,552 (1934). 

(20) L. Bertele, German Patent 441,594 (1925). 

(21) P. Rudolph, U. S. Patent 1,833,593 (1931). 

(22) A. Warmisham, U. S. Patent 1,926,569 (1933). 






1949 OBJECTIVE LENSES 99 



(23) A. Warmisham, British Patent 408,787 (1934). 

(24) R. E. Hopkins, J. C. Evans, W. Covell, and D. Feder, "Curved field lens 
and camera," J. Opt. Soc. Amer., vol. 38, p. 1102; December, 1948. 

(25) C. C. Minor, U. S. Patent 1,077,420 (1913). 

(26) G. F. Djian, French Patent 723,996 (1932). 

(27) J. M. Strang, U. S. Patent 2,417,330 (1947). 

(28) W. Schade, U. S. Patent 2,425,400 (1947). 

(29) H. W. Lee, U. S. Patent 2,100,291 (1937). 

(30) G. F. Djian, U. S. Patent 2,175,518 (1939). 

(31) Polaroid Corporation, Report on Optical Plastic Synthesis Fabrication 
and Instrument Design, Office of Scientific and Research Development Report 
No. 4417, 1945. 

(32) B. Schmidt, "Em Lightstarkes Komafreies Spiegelsystem," Zentralzeitung 
fur Opt. und Mech., vol. 52, pp. 25-26; January, 1931. 

(33) H. R. Schaltz, Zeit. Phys., vol. 79, pp. 843-851; November, 1932. 

(34) A. Sonnefeld, U. S. Patent 2,141,884 (1938). 

(35) J. Flugge, "Neuere Spiegelobjektive," Zeit. fur Instrumentenkunde, vol. 61, 
pp. 175-184; June, 1941. 

(36) K. Martin, J. Flugge, and H. Roll, U. S. Patent 2,229,302 (1941). 

(37) J. L. Houghton, U. S. Patent 2,350,112 (1944). 

(38) D. D. Maksutov, "New catadioptric meniscus systems," /. Opt. Soc. 
Amer., vol. 34, pp. 270-284; May, 1944. 

(39) A. Bouwers, "Achievements in Optics," Elsevier Publishing Company, 
New York, N. Y., 1946. 

(40) A. Bouwers, U. S. Patent 2,420,349 (1947). 

(41) H. F. Bennett, U. S. Patent 2,409,971 (1946). 

(42) A. Bouwers, U. S. Patent 2,448,699 (1948). 

(43) J. B. Baker, U. S. Patent 2,458,132 (1949). 

(44) C. G. Wynne, "New wide aperture catadioptric systems," (in English), 
Rev. d'Optiqiie, vol. 27, pp. 187-190; March, 1948. 

(45) D. Gabor, British Patent 544,694 (1942). 

(46) L. G. Henyey and J. L. Greenstein, "New types of fast camera," Amer. 
J. Roentgenology, vol. 59, pp. 565-569; April, 1948. 

(47) Yerkes Observatory Report on Wide Field Fast Cameras, Office of Scienti- 
fic Research and Development Report No. 4504, 1945. 

(48) A. Warmisham, U. S. Patent 2,306,679 (1942). 

(49) A. Warmisham, U. S. Patent 2,327,947 (1943). 

(50) A. Warmisham, U. S. Patent 2,336,379 (1943). 

(51) A. Warmisham, U. S. Patent 2,344,756 (1944). 

(52) A. Warmisham, U. S. Patent 2,380,887 (1945). 

(53) A. Warmisham, U. S. Patent 2,380,888 (1945). 

(54) R. J. Bracey, "A new//0.36 object-glass for stellar spectroscopy," Astro- 
phys. J., vol. 83, pp. 179-186; April, 1936. 

(55) D. O. Hendrix and W. H. Christie, "Some applications of the Schmidt 
principle in optical design," Sci. Amer., vol. 161, pp. 118-123; August, 1939. 

(56) J. G. Baker, "The solid glass Schmidt camera and a new type nebular 
spectrograph," Proc. Amer. Phil. Soc., vol. 82, pp. 323-338; April, 1940. 

(57) F. Nicoll, U. S. Patent 2,295,802 (1942). 






66th Semiannual Convention 
SOCIETY OF MOTION PICTURE ENGINEERS 

Hollywood-Roosevelt Hotel October 10-14, 1949 
Hollywood, California 


OFFICERS IN CHARGE 

EARL I. SPONABLE President 

LOREN L. RYDER Past-President 

PETER MOLE Executive Vice-President 

JOHN A. MAURER Engineering Vice-President 

CLYDE R. KEITH Editorial Vice-President 

DAVID B. JOY Financial Vice-President 

WILLIAM C. KUNZMANN Convention Vice-President 

ROBERT M. CORBIN Secretary 

RALPH B. AUSTRIAN Treasurer 

General Office, New York 

BOYCE NEMEC Executive Secretary 

HELEN M. STOTE Journal Editor 

WILLIAM H. DEACY, JR Staff Engineer 

SIGMUND M. MUSKAT Office Manager 

Chairmen of Committees for the Convention Program 

Convention Vice-President W. C. KUNZMANN 

Pacific Coast Section and Local Arrangements S. P. SOLOW 

Papers Committee Chairman N. L. SIMMONS 

Vice-Chairman, Hollywood L. D. GRIGNON 

Vice-Chairman, New York E. S. SEELEY 

Vice-Chairman, Chicago R. T. VAN NIMAN 

Vice-Chairman, Washington J. E. AIKEN 

Vice-Chairman, Montreal H. S. WALKER 

Publicity Committee Chairman HAROLD DESFOR 

Vice-Chairman, West Coast Announced Later 

Registration and Information C. W. HANDLEY 

Assisted by W. L. FARLEY and R. H. DUVAL 

Luncheon and Banquet J. P. LIVADARY 

Hotel Housing and Reservations WATSON JONES 

Membership and Subscriptions LEE JONES 

West Coast Vice-Chairman G. C. MISENER 

Ladies Reception Committee Hostess MRS. PETER MOLE 

Transportation Rail, Plane, Local HERBERT GRIFFIN 

Public-Address Equipment LLOYD T. GOLDSMITH 

Projection Program Committee 35-Mm R. H. McCuLLOUGH 

Assisted by Members of Los Angeles Projectionists Local 150 

Projection Program Committee 16-Mm H. W. REMERSCHEID, 

E. C. FRITTS 

100 



66TH SEMIANNUAL CONVENTION 
GENERAL INFORMATION 



101 



I EL RESERVATIONS AND RATES The Housing Committee, under 
Watson Jones, chairman, will make 

reservations for members and guests. Inform him at 1560 North Vine Street, 
Hollywood 28, California, of the accommodations you desire. He will book your 
reservations and confirm them. 
TRAVEL Make your train or plane reservations early because West Coast 

travel in October normally is quite heavy. 

LADIES AND GUESTS Members are encouraged to invite their friends to 
attend the convention. There will be eleven Tech- 
nical Sessions open to all who wish to be on hand, and for the ladies who accom- 
pany their husbands, the Ladies' Committee is arranging a week of sight-seeing 
and special events. 

RECREATION The identification cards issued to members and guests who 
register for the convention will permit them to attend Grau- 
man's Chinese and Egyptian Theaters of the Fox West Coast Circuit, the Holly- 
wood Paramount, the Pantages, and Warner Theaters, all of which are located 
on Hollywood Boulevard and near the hotel. Convention Headquarters will 
have a wealth of information on places to visit in or near the Los Angeles area. 
PAPERS PROGRAM Authors who plan to prepare papers for presentation at 
the 66th Convention should write at once for Authors' 

Forms and important instructions to the Papers Committee member listed below 
who is nearest. Authors' Forms, titles, and abstracts must be in the hands of 
Mr. Grignon by August 15 to be included in the Tentative Program, which will 
be mailed to members thirty days before the Convention. 



N. L. SIMMONS, Chairman 
6706 Santa Monica Blvd. 
Hollywood 38, California 

J. E. AIKEN, Vice-Chair man 
116 N. Galveston St. 
Arlington, Virginia 

LORIN GRIGNON, Vice-Chairman 
20th Century-Fox Films Corp. 
Beverly Hills, California 



E. S. SEELEY, Vice-Chairman 

Altec Service Corp. 

161 Sixth Ave. 

New York 13, New York 
R. T. VAN NIMAN, Vice-Chairman 

4501 Washington Blvd. 

Chicago 24, Illinois 
H. S. WALKER, Vice-Chairman 

1620 Notre Dame St., W. 

Montreal, Que., Canada 




EDWARD AUGER 



EDWARD AUGER, lifelong friend of the theater and retired em- 
ployee of RCA Theater Equipment Sales, suffered a heart 
attack on April 4, 1949, while attending the Convention of the 
Society of Motion Picture Engineers at the Statler Hotel in New 
York City. 

Mr. Auger got his start in the theater during the days of silent 
films and was an early independent producer of "Westerns." 
He joined RCA Photophone at its inception and remained with 
Theater Equipment Sales until his retirement in 1947. His wide- 
spread knowledge of the theater and friendships with exhibitors 
across the country made him a natural good-will ambassador for 
the Radio Corporation of America, and he became National Office 
Field Representative soon after his start with the company. He 
maintained contacts with exhibitors everywhere, and his liaison 
work was principally with chain- theater operators. 

On many occasions Mr. Auger was called out of retirement to 
handle special assignments for both RCA Theater Equipment Sales 
and RCA Theater Service. His co-operative efforts were well 
known among his many friends throughout the company. 

He joined the Society of Motion Picture Engineers as an Associate 
on April 3, 1934. 



102 



Book Reviews 



Comparative List of Color Terms 

A Report of the Inter-Society Color Council. Published, January, 1949, by 
the Inter-Society Color Council, Box 155, Benjamin Franklin Station, Washing- 
ton 4, D. C. Paper Bound. S 1 /^ by 11 inches. 94 pages. Price, $1.00 to mem- 
bers and delegates of the ISCC; $2.00 to nonmembers. 

This pamphlet is not intended as a final report on definitions; instead, it is 
meant to provide the basis for a thorough study of the subject among the member 
bodies of the Council and lead to a revision of this list that will provide official 
definitions upon which all can agree. 

Certain terminology, as applied to color, has taken on meanings peculiar to the 
art and science to which it is applied. Such meanings are, in some cases, not the 
same among various societies and have led to misunderstandings. This glossary 
lists the use of such terms and indicates to which group the meanings and defini- 
tions apply. Terms and phrases are listed alphabetically, followed by the defi- 
nition, with references. 

This report is well written and is edited by well-qualified people in eac|j field of 
color. It should be helpful to anyone working in the color field. 

JOHN L. FORREST 

Ansco 

Binghamton, N. Y. 



Physical Aspects of Colour, by P. J. Bouma 

Published (1948) by N. V. Philips Gloeilampenfabrieken, Eindhoven, The 
Netherlands. Distributed by Elsevier Publishing Company, Inc., 215 Fourth 
Ave., New York 3, N. Y. 263 pages + 12 pages + 13 pages tables and symbols 
+ 19-page bibliography + 4-page index. 113 illustrations, 6 x /4 X 9 1 A inches. 
Price, $5.50. 

Dr. Bouma's introduction to the physics and the measurement of color is a 
worth-while addition to our literature. In a book of some 300 pages, including a 
lengthy bibliography and competent index, the writer traces the subject of color 
from its fundamentals to its present position of international importance. The 
steps, the techniques, and their importance are clearly stated. This is followed by 
a regrettably brief mention of the relation of these subjects to the various fields of 
application. 

Dr. Bouma is at his best when he is discussing the historical background of the 
various controversies with which the subject has been burdened. Perhaps be- 
cause of the lack of a clear-cut theoretical basis, the subject of color has been 
much given to hearsay, whim, and casual discourse. All these are taken in the 

103 



Book Reviews 



writer's stride. He recognizes the contribution from both sides to an argument 
and is not deterred in his purpose, that of setting down the facts wherever they 
may lead. 

To American audiences the book will recommend itself chiefly by its rather com- 
plete and straightforward statement of the European point of view. Many people 
have thought on the subject of color and many different points of view have been 
expressed. It is good to find a writer who has set down the opinions in fair 
fashion with relatively little of judicial attitude. 

It could be wished, in some sections, that a little broader realization of the 
psychological implications were present, even in a book deliberately restricted to 
the physical point of view. Nevertheless, it is good to see a book which is re- 
stricted to this phase which at the same time recognizes other possibilities and 
other means of access to the subject. 

One regrets that its author is no longer with us. There are too few authors 
whose writings criticize the currently accepted ideas and at the same time freely 
state an opinion based on careful thought and deep historical knowledge. The 
book is definitely recommended reading for all who aspire to become familiar 
with ike peculiar but important and rapidly expanding field of color as a science. 

RALPH M. EVANS 

Eastman Kodak Company 

Rochester 4, N. Y. 



Better Color Movies, by Fred Bond 

Published (1948) by Camera Craft Publishing Company, 95 Minna Street, 
San Francisco 5, Calif. 156 pages + 3-page index. 70 black-and-white illus- 
trations, 16 color plates. &/ 4 X 9 J A inches. Price, $5.00. 

Fred Bond, who wrote a good book for still photographers entitled "Koda- 
chrome and Ektachrome from all Angles/' has written one for the amateur motion 
picture maker called "Better Color Movies." 

The book becomes rather technical in places for the average amateur, but the 
professional cameraman (and there are a number of them shooting 16-mm pro- 
fessionally) will find the book misleading in a number of places. Most amateur 
motion pictures consist of baby, family, and travel pictures. The amateur 
cinematographer will have little if any control over good or bad color schemes, and 
few of them will have any idea of the Munsell system of denoting color even after 
he reads the book. 

A good job has been done on the chapter, "Determining the Exposure," if the 
user can remember all the tables given, or consult the book before taking pictures. 
If he follows all the instructions for guessing the exposure, as explained by Mr. 
Bond, undoubtedly he will feel that he has used the mental-calculation method 
which is also described. 

The importance of color temperature is mentioned in a number of places 
throughout the book. Color temperature is important, but there are so many 
variables in color photography today that the amateur or even the professional 
104 



Book Reviews 



can do little about it. The amateur is warned not to use old photofloods and to 
be very careful with line voltage to avoid the brick-red flesh tones. Those pro- 
fessionals who have made accurate experiments with Kodachrome will not agree 
with Mr. Bond on all of these points. The majority of the amateurs taking 
motion pictures still have a great deal of trouble in securing correct exposures, 
even with the relatively simple exposure meters on the market, and if he attempts 
to calculate color temperature as well as exposure the average motion picture 
maker will probably become somewhat confused. 

I feel that Mr. Bond has made the mistake of many still photographers who have 
turned to motion pictures. He constantly makes still pictures instead of motion 
pictures. In fact, a number of the illustrations are pictures used in his book on 
still photography entitled, "Kodachrome and Ektachrome and How to Use It." 
Most of the illustrations on lighting are very good for still pictures, but are not 
suitable if any action is to take place. Unless there is action, it is not a motion 
picture. You get the feeling all through the book that he is trying to tell the 
motion picture maker how to take a number of beautiful photographs with no 
thought of continuity in action, writing, or composition. 

A chapter is devoted to theatricals and indoor sporting events. Mr. Bond also 
gives some rather definite exposure suggestions. Shots of theatricals and indoor 
sporting events have made the film manufacturers a great deal of money, but the 
number of bad pictures or no pictures far outnumber the good ones. For ex- 
ample, there are a few basketball courts in the country with enough light to obtain 
good pictures with the fastest black-and-white film. There are probably basket- 
ball courts somewhere in the country where color motion pictures can be shot, 
but we have seen it tried on a number of courts in black-and-white and we have 
even taken motion pictures for the National Tournaments. There is not any too 
much light for black-and-white even on these courts, which are supposed to be 
ideal. We, therefore, feel that color motion pictures on most courts is simply out 
of the question for the average amateur and the average basketball court. The 
average theatrical is just as hard to shoot. 

Anyone doing color photography and who likes to read will enjoy the book, 
even though he does not agree with it entirely. He should get some ideas, al- 
though we cannot say it is a "must" for every movie maker. 

LLOYD THOMPSON 

The Calvin Company 

Kansas City, Mo. 



105 



New Products 



Further information concerning the material described below can 
be obtained by writing direct to the manufacturers. As in the case 
of technical papers, publication of these news items does not consti- 
tute endorsement of the manufacturer's statements nor of his products. 



Spectra Direct Color 
Temperature Meter 

Photo Research Corporation, 15024 
Devonshire Street, San Fernando, 
California, announces the Spectra 
Direct Color Temperature Meter, de- 
veloped by Karl Freund. Color tem- 
perature of incident light is measured 
by pointing the side containing a 
photoelectric cell toward the camera or 
source of light, and turning the dia- 
phragm ring until the meter needle 




comes to a reference mark. When a 
trigger is pressed, the color tempera- 
ture is indicated directly on a scale 
reading from 2000 to 30,000 degrees 
Kelvin. 



Automatic Tristimulus Integrator 

General Aniline and Film Corpora- 
tion, 230 Park Ave., New York 17, 
N. Y., and Librascope, Inc., Burbank, 
California, recently introduced an 
automatic tristimulus integrator to be 
used with the General Electric re- 
cording spectrophotometer. 

The primary elements in the me- 
chanical computer are ball and disk 
integrators. Wavelength and re- 
flectance, or transmittance, of the sam- 
ple are fed into the computer by servo- 
mechanisms. The only modification 
required on a standard spectrophotom- 
eter is the installation of two Selsyn 
transmitters, the removal of a section 
of panel, and installation of two rails. 
Normal operation of the spectropho- 
tometer is not affected. 

While a sample is being measured in 
the spectrophotometer at either high 
or low speed, the integrator automati- 
cally computes the tristimulus values 
to a precision of about 0.0005. 
When the curve is completed, the 
values are read from three counters on 
the computer, the counters are reset to 
zero, and the next sample may be run. 
Thus tristimulus values are obtained 
with practically no additional time be- 
yond that normally required for draw- 
ing the spectrophotometric curve. 



106 



Journal of the 

Society of Motion Picture Engineers 

VOLUME 53 AUGUST 1949 NUMBER 2 

PAGE 

Engineering Techniques in Motion Pictures and Television 

ALFRED N. GOLDSMITH 109 

Motion Picture Laboratory Practice for Television 

ARTHUR J. MILLER 112 

Sound-on-Film Recording for Television Broadcasting 

CLYDE R. KEITH 114 

Television-Film Requirements G. DAVID GUDEBROD 117 

Will Film Take Over the Television Commercial? : 

JOSEPH A. MORAN 120 

Discussion Television Forum 124 

Progress Report Theater Television BARTON KREUZER 128 

Television Pickup for Transparencies. . . .ROGER D. THOMPSON 137 
Use of 35-Mm Ansco Color Film for 16-Mm Color Release Prints . 

REID H. RAY 143 

Direct-Positive Variable-Area Recording with the Light Valve 

LEWIS B. BROWDER 149 

35-Mm and 16-Mm Portable Sound-Recording System 

E. W. TEMPLIN 159 
Demineralization of Photographic Wash Water by Ion Exchange 

HARRY P. GREGOR AND N. N. SHERMAN 183 

Meetings of Other Societies 192 

Film Vaults: Construction and Use JOHN G. BRADLEY 193 

66th Semiannual Convention 207 

John H. Kurlander 210 

Proposed Standard for 35-Mm Sprocket Holes . .211 

Section Meeting 211 

New Products 212 

ARTHUR C. DOWNES HEIIEN M. STOTE NORWOOD L. SIMMONS 

Chairman Editor Chairman 

Board of Editors Papers Committee 

Subscription to nonmembers, $10.00 per annum; to members, $6.25 per annum, included in 
their annual membership dues; single copies, $1.25. Order from the Society's General Office. 
A discount of ten per cent is allowed to accredited agencies on orders for subscriptions and 
single copies. Published monthly at Easton, Pa., by the Society of Motion Picture Engineers, 
Inc. Publication Office, 20th & Northampton Sts., Easton, Pa. General and Editorial Office, 
342 Madison Ave., New York 17, N. Y. Entered as second-class matter January 15, 1930, 
at the Post Office at Easton, Pa., under the Act of March 3, 1879. 



Copyright, 1949, by the Society of Motion Picture Engineers, Inc. Permission to republish 
material from the JOURNAL must be obtained in writing from the General Office of the Society. 
Copyright under International Copyright Convention and Pan-American Convention. The 



Society of 

Motion Picture Engineers 

342 MADISON AVENUE NEW YORK 17, N. Y. TEL. Mu 2-2185 
BOYCE NEMEC . . . EXECUTIVE SECRETARY 

OFFICERS 

1949-1950 



PRESIDENT 
Earl I. Sponable 
460 W. 54 St. 
New York 19, N. Y. 

EXECUTIVE 
VICE-PRESIDENT 
Peter Mole 

941 N. Sycamore Ave. 
Hollywood 38, Calif. 



PAST-PRESIDENT 
Loren L. Ryder 
5451 Marathon St. 
Hollywood 38, Calif. 

EDITORIAL 
VICE-PRESIDENT 
Clyde R. Keith 
120 Broadway 
New York 5, N. Y. 



SECRETARY 
Robert M. Corbin 
343 State St. 
Rochester 4, N. Y. 

CONVENTION 
VICE-PRESIDENT 
William C. Kunzmann 
Box 6087 
Cleveland 1, Ohio 



1948-1949 



ENGINEERING 
VICE-PRESIDENT 
John A. Maurer 
37-0131 St. 
Long Island City 1, N. Y. 



TREASURER 
Ralph B. Austrian 
25 W. 54 St. 
New York 19, N. Y. 



1949 

FINANCIAL 
VICE-PRESIDENT 
David B. Joy 
30 E. 42 St. 
New York 17, N. Y. 



1948-1949 

Alan W. Cook 
4 Druid PI. 
Binghamton, N. Y. 



Lloyd T. Goldsmith 
Warner Brothers 
Burbank, Calif. 



Paul J. Larsen 
508 S. Tulane St. 
Albuquerque, N, M. 



Gordon E. Sawyer 
857 N. Martel Ave. 
Hollywood 46, Calif. 



Governors 
1949 

James Frank, Jr. 
1310 Peachtree Battle 

Ave., N. W. 
Atlanta, Ga. 

William B. Lodge 
485 Madison Ave. 
New York 22, N. Y. 

William H. Rivers 
342 Madison Ave. 
New York 17, N. Y. 

Sidney P. Solow 
959 Seward St. 
Hollywood 38, Calif. 

R. T. Van Niman 
4431 W. Lake St. 
Chicago 24, 111. 



1949-1950 

Herbert Barnett 
Manville Lane 
Pleasantville, N. Y. 



Fred T. Bowditch 
Box 6087 
Cleveland 1, Ohio 



Kenneth F. Morgan 
6601 Romaine St. 
Los Angeles 38, Calif. 



Norwood L. Simmons 
6706 Santa Monica Blvd. 
Hollywood 38, Calif. 



Engineering Techniques 

in Motion Pictures and Television 5 

BY ALFRED N. GOLDSMITH 

CONSULTING ENGINEER, NEW YORK 17, NEW YORK 



IN THE FOLLOWING BRIEF SUMMARY it is feasible only to outline 
problems and processes, and primarily to stimulate discussion. 
Actually the subject matter of this short commentary would require, 
for adequate treatment, a number of large and impressive volumes. 

Properly handled, the television broadcasting of a film presentation 
should be identical (so far as the audience is concerned) with a live- 
talent program. There are some incidental technical and economic 
advantages inherent in the use of film. These include ease of repeti- 
tion of the program, the possibility of ready cutting and editing, the 
certainty of program quality, the predictability of the program, and 
the like. 

Adequate film presentations in television imply, however, that the 
film picture and sound shall exceed in general quality the capabilities 
of the television system. In other words, the bottleneck in perform- 
ance should reside in the television transmission and reception, 
not in the film recording. Accordingly the film images must have 
resolution and gradation range superior to that of the television 
system. The sound recording similarly must excel in fidelity and in 
low noise level. 

Available data indicate that 35-mm film, used for pictorial pur- 
poses, would be more than adequate. Sixteen-millimeter pictures, 
made as reductions from original 35-mm negatives, are largely satis- 
factory. More nearly marginal are 16-mm positives made from 16- 
mm negatives, particularly if these negatives are derived directly 
from a television system by kinescope or picture-tube recording. 

So far as sound reproduction is concerned, 35-mm records running 
at 90 feet per minute are satisfactory. Sound reproduction from 16- 
mm film, under existing circumstances, fluctuates about an adequacy 
level. 

* Presented April 4, 1949, at the SMPE Convention in New York. 

AUGUST, 1949 JOURNAL OF THE SMPE VOLUME 53 109 



110 GOLDSMITH August 

The preceding comments refer specifically to 16-mm and 35-mm 
film used by available personnel in everyday available equipment, 
under normal circumstances, and with routine commercial processing 
of the film negatives and positives. That is, these comments apply 
to everyday conditions as now experienced. 

Once a film transcription of picture and sound is available, it can be 
used to modulate the image transmitter by one of several available 
methods. Thus, the pictures may be intermittently projected upon 
the screen of a camera tube, using as required a regime suitable for 
converting 24 frames per second on the film to 60 interlaced fields per 
second of the television transmission. 

Alternatively, the film pictures may be scanned by a flying light 
spot, which is itself a focused image of a raster-forming spot on a low- 
persistence, high-intensity picture tube. 

It has also been suggested that nonintermittent projection of the 
film upon the camera tube photosensitive surface be used. This proc- 
ess has not as yet found commercial exploitation. 

The film transcription itself may be made in a variety of ways, two 
of which may be mentioned. The most obvious and direct method of 
producing a film transcription is by actual photography of the face of a 
monitor picture tube or kinescope which is reproducing the program 
to be recorded. This method has the advantages of high speed, 
simplicity, and low cost. It has the limitations that the record neces- 
sarily can be no better than the image produced by the electrical por- 
tions of the television system up to and through the monitor kine- 
scope. Further, it lacks any capabilities of cutting, editing, or sub- 
stantial and flexible revision of the recorded material. As a result, 
this method is a present-day expedient. It produces program material 
fluctuating around an acceptable level. 

Presumably direct kinescbpe recording could be improved if certain 
fairly radical steps were taken. For example, if high-resolution and 
wide-gradation-range television systems were used between the 
studio camera and a precision monitor kinescope, the picture available 
for photography would be adequate or more nearly so. Such a pro- 
cedure might well justify the use of 35-mm film for recording the 
picture, at least for the transcription negative. This would enable 
the full capabilities of such an evolved television system to be realized 
and would provide film transcriptions which might well be, as pre- 
viously suggested, better than the conventional television broadcast- 
ing system over which they were later to be transmitted. 



1949 MOTION PICTURES AND TELEVISION 111 

A second method of producing film transcriptions is the obvious one 
of direct photography in the studio along more or less conventional 
motion picture lines. One necessary exception to this statement 
would be the requirement that economy of operation would neces- 
sarily be stressed to a far greater extent than is customary in motion 
picture practice. Studio photography of the program yields superioi 
picture quality, greater ease of cutting and editing, enhanced flexi- 
bility in production, and the possibility of retakes as required. How- 
ever, production costs will, at best, be considerably increased when 
this method is used, and the speed of production will be appreciably 
reduced. 

Considering comparatively both 35-mm and 16-mm films, as used 
in television, there is something to be said in favor of each of these. 
The obvious ease of handling 16-mm films, and the correspondingly 
lower equipment, film, and processing costs are definitely advanta- 
geous. On the other hand, the improved quality, increased reliability, 
and the more highly developed 35-mm techniques as contrasted with 
those available for 16-mm film swing the scale back toward, or even 
beyond, a level position. 

It will, therefore, be interesting to observe the future developments 
in this "millimeter contest," so to speak. So far as the recording of 
actual program material is concerned, this struggle may be vigorous 
enough. It will likely be even more strenuous in relation to the 
customary and much cherished commercial announcements which, of 
necessity, are the "sponsor's pride." 

It is urged that present-day practices be not regarded as crystal- 
lized and permanent. It is rather suggested that alternative methods 
for the production of film transcriptions on various sizes or gauges of 
film be thoroughly and continuously explored. It may thus result 
that television, five years in the future, shall continue to please its 
audiences and shall utilize programs on film most effectively and 
economically, all factors being considered. 






Motion Picture Laboratory 
Practice for Television* 

BY ARTHUR J. MILLER 

CONSOLIDATED FILM INDUSTRIES, NEW YORK 19, NEW YORK 

THE USE OF MOTION PICTURE FILMS in television has brought with 
it a variety of problems, both for the producer or the user and for 
the laboratory making prints for such use. These remarks will be con- 
fined to the subject of picture quality on 16-mm films for use in 
television. 

There are three controllable factors which can be considered in the 
production of an acceptable film for this use: definition, contrast of 
the print, and print density. 

The definition of the print is first governed by the definition of the 
material from which the print is made. No print can be sharp if the 
original material used is lacking in definition because of improper 
focus of the camera, dirt, or moisture on the lenses, or any one of many 
factors. 

Assuming that we have a negative or other original material which 
has as good definition as can be obtained, then the factors controlling 
the ultimate definition of the print used for television are limited to 
the equipment used in the laboratory, and the inherent limit of defi- 
nition in the stock used for the print. 

If the print is made by reduction from a 35-mm negative, it is essen- 
tial that the printer used for this purpose be maintained in the highest 
state of mechanical and optical perfection. 

Two types of printers are commonly used when making contact 
prints. One is the continuous printer which is most commonly used in 
all production work and in which the negative and positive films are 
moved continuously past an aperture during exposure, while being 
carried on a sprocket. 

Contact and definition in this type of printer are dependent largely 
on the shrinkage of the negative in relation to the positive and the 
amount of curl inherent in the two films. Tension is applied during 
printing to keep these effects at a minimum, and it goes without 

* Presented April 4, 1949, at the SMPE Convention in New York. 
1 12 AUGUST, 1949 JOURNAL OF THE SMPE VOLUME 53 



TELEVISION LABORATORY PRACTICE 113 

saying that the sprocket on which the films are printed must be cut 
to the highest degree of mechanical perfection possible. 

Unless all these factors of shrinkage and curl happen exactly to 
match with each other and the design of the sprocket, it is possible 
to secure better definition on prints made on a step printer, in which 
each frame is printed separately, and in which the negative and 
positive films are held in tight contact during exposure. 

The other main factor, in securing high definition, is the maximum 
resolving power of the positive film used. It has been remarked that 
if this resolving power is greater than that of the television system 
the other factors are immaterial. It is not believed that this is the 
fact, but that all of the definition possible should be saved in each of 
the steps necessary in bringing a motion picture to the television 
screen. 

Some of the prints shown were made on continuous-type printers 
and others were made on highest definition step-type printers. Some 
prints on each type printer were made on fine-grain release positive, 
and some were made on fine-grain duplicating positive, which has the 
highest resolving power of the commercially available motion picture 
films. 

This film also has the advantage of producing excellent quality 
when developed in the manner that these prints were made, that is, 
to a gamma of approximately 2.10, producing a good tone range on 
varying types of scenes. 



Sound- on- Film Recording 
for Television Broadcasting* 

BY CLYDE R. KEITH 

WESTERN ELECTRIC COMPANY, NEW YORK 5, NEW YORK 



REMARKS ARE CONFINED for the most part to problems of 
J_ sound on 16-mm film, since such films are of greatest economic 
importance to the television broadcaster. 

There are three principal bottlenecks tending to degrade the 
quality of sound obtained from 16-mm films in television 
broadcasting. 

1 . 1 6-mm film processing is generally inferior to 35-mm processing, 
resulting in more noise and distortion than would be present if equally 
good processing were available for 16-mm films. This is shown by the 
tendency of Hollywood studios to record sound on 32- to 35-mm film so 
that it can be processed in 35-mm developing machines. 

2. 16-mm printers frequently introduce distortion and flutter. 
Good 16-mm printing requires a higher degree of precision in the 
printer than is required for 35-mm printing. 

3. Most 16-mm sound-and-picture projectors do not have the 
electrical, mechanical, and optical accuracy required to give the 
best results, or the mechanical sturdiness to maintain optimum ad- 
justments over a long period of steady use. 

Most of the above deficiencies arise from cut-price competition in 
the amateur and educational fields. Considerable improvement 
should result if methods and equipment used in the 35-mm field are 
adopted. 

EFFECT OF LACK OF ADJUSTMENT 
OF REPRODUCER ON SOUND QUALITY 

1 . Frequency Response 

Some commercial 16-mm reproducers are built with excessive loss at 
frequencies over 3 to 4 kilocycles. The output at 5 kilocycles may be 
as much as 10 to 15 decibels below that at 1 kilocycle. This droop may 
be introduced intentionally on the assumption that the reproduction 

* Presented April 4, 1949, at the SMPE Convention in New York. 
114 AUGUST, 1949 JOURNAL OF THE SMPE VOLUME 53 



SOUND ON FILM FOR TELEVISION 115 

of noise and distortion products above 4 to 5 kilocycles degrades the 
sound quality more than it would be improved by reproducing the 
signal uniformly up to say 7 kilocycles. While this may be a reason- 
able assumption for many 16-mm films in circulation today, it does 
not allow for improvement as better recording and printing techniques 
are developed. It would be preferable to use a scanning system and 
amplifier which would provide essentially uniform response to at least 
7 kilocycles and then use a suitable low-pass filter whose cutoff fre- 
quency could be adjusted depending on the noise and distortion on a 
particular record. This is similar to the practice used in broadcasting 
phonograph records. A test film such as Z22.44-16-mm Multifre- 
quency Test Film should be used for determining reproducer 
response. 

2. Scanning-Beam Focus 

An out-of-focus condition reduces high-frequency response. Some 
reproducers focus in the center of the film to take care of both stand- 
ard and nonstandard emulsion positions. This means neither position 
is quite right and may give a loss of about 3 decibels at 7 kilocycles 
depending on the optical system. Out-of-focus by thickness of film 
may cause a loss of 10 decibels at 7 kilocycles. 

The projector should have quick change of focus between front and 
back surface of film. Focus should be checked periodically with 
Z22.42-16-Mm Sound Focusing Test Film, 7000- Cycle Laboratory 
Type. 

3. Scanning-Beam Azimuth 

Azimuth error causes loss at high frequencies similar to loss caused 
by slit width. It also introduces wave-form distortion in reproducing- 
variable-area sound records. For example, if azimuth is out by width 
of slit (0.5 mil), second harmonic of 3600 cycles would be about 12 per 
cent for area tracks. Azimuth should be checked with above Z22.42 
Test Film. 

4- Scanning-Beam Position 

Improper position of scanning beam relative to sound track may 
cause noise on density films or both noise and distortion on area films. 
Scanning beam too close to the edge of the film causes random noise 
while beam too far from the edge may produce 24-cycle noise caused 
by picture-frame lines. 



116 KEITH 

With variable-area sound tracks, displacement in either direction 
will also cause severe distortion at high amplitudes because of sharp 
cutoff of wave peaks. Track position should be checked by means of 
Z22.57-16-Mm Buzz-Track Test Film. 

5. Uniformity of Illumination 

Nonuniformity of scanning-beam illumination has no effect on a 
variable-density track, but may introduce considerable distortion in 
variable-area tracks. Harmonic distortion may be shown to be quite 
low for any reasonable nonuniformity of illumination. For example, 
with a bilateral track and symmetrical (parabolic) nonuniformity 
20 per cent brighter in the center than at the sides, the second har- 
monic is about 3 per cent and the third about x /2 per cent. However, 
intermodulation of high and low frequencies is much higher. With the 
same light distribution intermodulation would be 15 to 20 per cent. 

In some machines distortion is also produced in area tracks by 
nonuniform sensitivity of the cathode of the phototube. This occurs 
where the optical system is such that the illuminated area of the 
cathode varies as the width of the track. Intermodulation as high as 
60 per cent has been measured because of this effect. No standard 
test film is now available to measure intermodulation caused by scan- 
ning deficiencies, but such a film can be made without difficulty. 

6. Flutter 

One of the most noticeable defects in the reproduction of films over 
television at this time is flutter. The flutter frequently is very much 
greater than would be tolerated in even the smallest theater. While it 
is possible that the flutter may be in the film, it may also be in the 16- 
mm reproducer. This need not be the case since it is possible to build 
machines in which the flutter is consistently below audible levels. 
Although methods of flutter measurement have not been finally 
standardized, methods and equipment are well known in the film in- 
dustry. A flutter test film Z22.43 is available for this purpose. 



Tele vision- Film Requirements 

BY G. DAVID GUDEBROD 

N. W. AYER AND SON, NEW YORK 20, NEW YORK 



PRINTED MATERIAL describing this forum mentions industrial, 
_ educational, institutional, commercial, and promotional films as 
well as entertainment films. It implies that they are all frequently 
used for television programming. Actually, however, straight in- 
dustrial or institutional films are so unadaptable and so specialized 
that in the author's opinion they can be safely ignored as a factor in 
television programming. In order to clarify and simplify things a 
little, the films covered in this paper are primarily entertainment 
films the type of films sought when building a television program to 
sell goods for a sponsor. 

Motion picture production requirements so far as television is 
concerned are almost like any other film requirements: first, the 
films must have box-office appeal; second (and this is a variation) r 
continuity; third, technical excellence; and fourth, the price must be 
right. 

These four main qualifications must be examined from an ad- 
vertiser's standpoint an advertiser who is looking at television as a 
new medium of mass communication. 

An advertiser is going to insist that his television films have box- 
office appeal for the very simple reason that he wants a big audience 
the larger the better. No clients have ever complained about having 
too large an audience, but television must have a very special sort of 
box-office appeal. The film must be created to speak to three or four 
people in a living room. It must have a certain warmth and intimacy. 
Films for theatrical distribution depend to a great extent on awaken- 
ing a crowd reaction. A television film plays to no crowd. It does not 
even have a studio audience to lean on. It must reach directly into 
the home and sing a song or spin a yarn to three or four people, not 
three or four thousand. 

How can one tell whether a television film has this type of box- 
office appeal? Probably no one can do it consistently, but one must 
keep trying to capture it when possible. 

* Presented April 4, 1949, at the SMPE Convention in New York. 

AUGUST, 1949 JOURNAL OF THE SMPE VOLUME 53 117 



118 GUDEBROD AugUSt 

The second qualification is continuity. Box-office appeal gets the 
audience, continuity holds it! Advertisers have long since learned 
that the audience likes to have something familiar in their entertain- 
ment week after week. To the author's knowledge a successful radio 
or television program has never existed without continuity of one kind 
or another. Sometimes it is no more than a make-believe theater such 
as the Kraft Television Theater, The Philco Playhouse, or the Ford 
Theater. Still another type of continuity is achieved by the use of a 
single recurring character such as the Bookshop Man in the current 
Lucky Strike series. And sometimes there is a continuity of story and 
cast as in the live Goldbergs or the filmed Adventures of Eddie Drake. 
In any case, there is a need for something or someone which the 
audience can remember from week to week. 

Now for the third point technical excellence. Here again, it is 
thought that there is a difference in technical excellence for normal 
theatrical use and technical excellence for television use. One is not of 
lower quality than the other, they are merely different. Since 1939 
N. W. Ayer has been using films in television with varying degrees 
of success. At first the Company was forced by economies to cut up 
old prints and splice odds and ends together to tell a commercial 
story. This brought a number of horrible experiences, and many a con- 
ference was held with television engineers trying to find out what was 
wrong. The lesson was learned the hard way, simply because in those 
days there were somewhat less than five thousand sets in the whole 
United States, and no advertiser could afford to spend more than 
print costs to try this medium. The approach being made here today 
to the problems of lighting, sound recording, and printing for televi- 
sion films is one of the best things that can possibly be done for tele- 
vision. Without this sort of approach, films never will become as im- 
portant a factor in television as they should. To be technically ex- 
cellent a television film must be made for television in the first place. 
That means that the writer, director, cameraman, cutter, and labo- 
ratory technician must work to new standards, television standards. 

Finally, there is the question of price. Two years ago with a brash- 
ness born of enthusiasm for the film medium in television, the author 
suggested in a forum meeting that films for television could be pro- 
duced at a considerably lower price than most people thought possible. 
The basic idea was to recognize the limitations of television, the 
slower pace, the difference in lighting and finally to preplan films on a 
sort of assembly line. At that time, the suggestion was regarded, in 



1949 TELEVISION-FILM REQUIREMENTS 119 

certain quarters, as heresy and high treason. Today, it is being 
me. 

The advertiser is vitally interested in price. He generally knows 
)w much he can afford to spend to reach a thousand prospects, and he 
itches this cost per thousand with an eagle eye. In the author's 
)inion it will be found that it is going to be worth more to reach a 
lousand customers via television than it is to reach them by other 

lia. 

Someone is going to say "What is the right price?" And the only 
answer that can be given is an evasive one, "That depends!" It de- 
pends first of all on how much an advertiser can afford to spend to 
reach prospective customers. It depends on how widespread will be 
his use of the film. It depends on what television can do for his busi- 
ness. All of these variables must be taken into account by any good 
advertising man before he can say "This film is a good buy for 
Client A." 

In the author's opinion the Lucky Strike series of films has all four 
requisites for good television film production box office, continuity, 
technical television excellence, and a proper price. 

The twenty-six stories which comprised this series were chosen from 
world-famous anthologies. They must be good box office, people 
must like them, because they have been selling well for years, read 
and reread by hundreds of thousands of people. 

And here is continuity in the Bookshop Man, a warm and intimate 
person whom you grow to like after a while. Sure, he's a bit of a 
character but no doubt people like him just because he is a character. 
Technical excellence for television? The author thinks so, although 
in the early films of the series there were troubles with halation and 
edge flare and too much contrast and bad lighting. But those things 
are being corrected. 

And the price? It is as right as any television price can be today. 
With the show running each week in 29 markets and with its rating in 
the thirties, the cost per thousand is satisfactory. 



Will Film Take over 

the Television Commercial?* 

BY JOSEPH A. MORAN 

YOUNG AND RUBICAM, NEW YORK 17, NEW YORK 



PEOPLE IN THE ADVERTISING RusiNESs are convinced that the 
amount of film used for television commercials will be determined 
largely by the way film does its job. Any commercial is supposed to 
sell goods, and to sell goods over television, many of the same things 
are done that sell goods over the counter or from door to door or over a 
desk. As many contacts as possible are made with prospects. They 
must be interested in what a product can do for their welfare. Show 
them the product. Demonstrate the way it works. And if possible, 
try to make friends while doing this. 

The interest in television at present is so great that probably it is 
easy to make contacts with prospects. But unless television com- 
mercials start with good showmanship, the very intensity of interest 
may work against them. 

When the commercial flickers on, that CAN be the cue for Dad to 
tell Mother about the funny thing that happened to him on his way to 
the office or ploughshed today or for sonny to sneak the dial 
over for a minute to see how Cassidy is hopping along or even for 
someone to leave on an errand. So it helps if the television commer- 
cial flows smoothly into the program. 

For instance, most people would agree that film gets a black mark 
when the quality does not even remotely resemble live camera pickup. 
That tips off the commercial and cuts down listening and viewing. 
Also, the quality is often worse, and something, maybe the film pro- 
jector, sometimes causes electrical differences that seem to throw off 
the pattern on the viewer's set. 

Of course, these technical matters, such as contrast and density, 
should be studied carefully by experts if advertisers will continue to use 
film commercials. 

Skillful leads into a commercial and a good commercial itself are 

* Presented April 4, 1949, at the SMPE Convention in New York. 
120 AUGUST, 1949 JOURNAL OF THE SMPE VOLUME 53 



FILM AND TELEVISION COMMERCIALS 121 

very important, but they will not help if listeners see a commercial 
coming. One of the fascinating things about television, viewers say, 
is the idea that it is happening right before your eyes. Film that is 
obviously film may spoil that illusion. 

If more and more film is to be used for television commercials, the 
first thing to concentrate on is technical quality, and this means not 
just film that looks well on a motion picture screen, but film that will 
look well on the customer's set. There is a big co-operative job to be 
done here between the advertising agency, the film experts, and the 
television engineers. 

Now that contact has been made with a customer, he must be sold. 
Interest him in what is to be sold, then show it to him. Right here, 
says the advertising man, is why television was born, and why he 
is looking to film for the best pictures possible. To the advertiser, 
those three minutes of commercial are three golden minutes. They are 
the reason for the whole show, and the entire investment. So the 
product has to look just right, and again that means films that televise 
right. 

After the product is shown, probably it is to be demonstrated. 
That is where film has certain advantages. The demonstration CAN 
go wrong if the commercial is live. And has. On one show, for a 
horrible example, the high-pressure hose did not squirt and it was only 
the foresight of a production man who had provided a bottle of seltzer 
water that saved everyone an embarrassing moment. Things have 
always gone wrong in radio, and television is no exception. But with 
film, the mistakes go on the cutting-room floor. This dependability 
of film will help make it popular for television commercials. 

Before television, advertisers kept saying that radio was great, but 
that one thing it could not do was show the product. With television, 
the skeptics are asking if television can show the product as clearly and 
as beautifully as printed advertising. 

There is no color, but probably everyone will agree that at times the 
best television reproduction is nearly equal to good magazines for 
tones. Advertisers will turn to film only if it gives them a picture 
every bit as good and better than the live pickup. 

The author was asked about what the advertiser and his agency 
consider important in film commercials. Probably product plus 
people is one thing, good pictures of the product in action in relation 
to people, and the other is showmanship plus salesmanship, good 
staging plus good selling. 



122 MORAN August 

The author also was asked about the length of television-film com- 
mercials. The networks have established this rather closely. Spots, 
commercials made and run independently of sponsorship of a pro- 
gram, are usually fixed for television at twenty seconds for short 
spots, one minute for long spots. The twenty-second length is becom- 
ing more and more popular, probably because it can be put in between 
the important programs ; and because its position can be guaranteed 
and not be pushed off when a sustaining show becomes a sponsored 
one. 

On programs, the usual total time is three minutes for an evening 
half-hour show. Normally there are two main commercials of a little 
over a minute each and a short opening and closing. The openings 
usually will not run more than fifteen or twenty seconds because the 
opinion of most television men is that it is very important to get a 
show off to a fast start. The main commercials and the openings and 
closings together use up the total three minutes. Three minutes is 
about 10 per cent of the program time and, with slight differences, 
that proportion holds for almost all radio and television program- 
ming. Therefore it is important to make every second of commercial 
count. 

There has been some discussion of using one long rather than two 
short commercials on television programs but the eventual outcome of 
this is unknown. In radio, the Nielsen charts show the way in which 
customers tune in and out of a program and prove that more people 
will be reached if the three minutes of commercial are broken into 
several units and distributed at different points throughout the pro- 
gram. Probably this will hold true for television, too, and the single 
long commercial will not be used very frequently by advertisers. 

One question is about the re-use of film commercials, because film 
commercials are expensive to make, especially good ones. Some com- 
mercials, of course, can be used again and again in exactly the same 
way. Some never can be used again. Probably most advertisers 
would be satisfied to make but three commercials in the course of a 
year, and then repeat the group three or four times to cover their 
program period. 

Anyone who wants to do a little mathematics can decide what this 
means in terms of film footage. At the present moment television 
stations in New York, which is the most highly developed area, are on 
the air an average of forty-seven hours per week. If this increases to 
something like twenty hours (1200 minutes) a day of operation, and if 



1949 FILM AND TELEVISION COMMERCIALS 123 

5 per cent (60 minutes) of the twenty hours a day are represented by 
commercials on film, then in 365 days, at 90 feet per minute and 
divided by four to allow for repetition, 200 stations will use 98,550,000 
feet of film. (The station count is low because it is assumed that many 
commercials will be transmitted by network.) At the present mo- 
ment, New York stations are using an average of 26 per cent film, but 
this includes old film run as entertainment. 

From the advertiser's standpoint, the physical characteristics of 
film commercials will become important. Safety film is a great con- 
venience. Thirty-five-millimeter film shows some signs of becoming 
standard because of the extra quality it provides. At the present mo- 
ment screenings for agency personnel and for clients are usually done 
by means of 16-mm prints which can be shown in any office. Perhaps 
this will continue to be easier than providing the more expensive 35- 
mm projection equipment. 

Finally, whether it is on film or live, the television commercial is not 
just on the screen, it is also on the spot. New research measurements 
are already being developed to tell whether the commercial is doing 
this job. These are the like and dislike charts made by groups of 
people holding little electric switches that show how they react to 
every single minute of a program, including the commercials. 

There are tests for remembering, and for the extent to which tele- 
vision viewers have a better notion of products advertised to them. 
There are methods available for making direct checks in the homes of 
listeners and measuring the ultimate effectiveness of the commer- 
cial. This means there must be a whole new technique for film com- 
mercials, and that television technique undoubtedly will need the 
services of dozens of specialists just as specialists are needed to get the 
best quality in magazine reproduction. Television is a new field, but 
it comes into action against highly developed competition, and that 
means there must be top results right away. There is apparently not 
going to be in television a long period of infancy such as there was in 
radio. We all must work together to make film commercials tech- 
nically and creatively the equal of any other type of advertising. 

It is certain that the same kind of ingenuity, inventiveness, re- 
search, experience, and judgment which made radio commercials so 
effective so quickly, will make them even more effective in television, 
even more quickly. 




Television Forum 



Note: After the delivery of the papers on the Television Forum, Moder- 
ator Hyndman called for discussion. As this issue of the Journal goes to 
press, the paper by Richard Blount, "Studio Lighting for Television," and 
that by Edmund A. Bertram, "Motion Picture Laboratory Practice for Tele- 
vision," are not yet available, but it is expected that they will be published 
in later issues. 

DISCUSSION 

MR. ROCKMORE: Mr. Gudebrod mentioned the amount which the advertiser 
can afford to pay. Should not the comparative effectiveness of television versus 
other media be considered in considering price? 

MR. G. D. GUDEBROD: I think I indicated we suspect from an advertising 
standpoint that it is going to be worth more to reach any given thousand people 
in television than by any other medium. Currently, however, I do not believe 
there is enough qualitative information of that kind to say what that factor is, 
whether it is P/s X or 2 X or 3 X. As the medium grows up a little, I think we 
shall have more concrete figures so we can say instead of, as an advertiser will 
say, $6.00 a thousand, maybe we shall say he should pay $10.00 a thousand. As 
yet we have not gone far along the road. 

DR. ALFRED N. GOLDSMITH: We have some data on sponsor identification and 
product identification ratios as compared, for example, to those for standard 
radio, and the like, and we are beginning to get adequate data. And they do 
indicate a distinct superiority in impact value of television. 

MR. E. F. ZATORSKY: This is directed specifically to the Technical Committee. 
When are they going to set up specifications on the television apertures and the 
like so we shall not be penalized the same as we are in standard motion picture 
aperture so far as the microphone goes, in order to make motion pictures cheaper 
for television, which would be the answer to Mr. Gudebrod's specification. 

MODERATOR D. E. HYNDMAN: Unfortunately, there is no direct answer at pres- 
ent but work on standards is in process. 

MR. ZATORSKY: Do you not think the Technical Committee ought to set up a 
recommendation? 

MODERATOR HYNDMAN: It has been discussed, and I believe that would be in 
the hands of the Committee on Television. John Maurer, Engineering Vice- 
President, is here; perhaps he will choose to answer. 

MR. JOHN A. MAURER: I should like to point out that in the booklet on films 
for television which was issued a short time ago by our Television Committee, 
and which has by now been rather widely circulated, there is specific mention 
made of the ratio of the motion picture frame that is to be expected to be utilized 
by the television picture. . At the moment, I do not remember just what the 
figure is, but it is in there in quite a specific form. It has not as yet received the 
sanction of a standard, but doubtless it will work that way in the future. 

I should like to add a couple of footnotes to some of what Dr. Goldsmith said 
and likewise to Mr. Hyndman's remarks with reference to the projection here. 

Dr. Goldsmith made the comment that as television improves, and when a 
124 



TELEVISION FORUM DISCUSSION 125 

wider frequency range may be transmitted to the television tube that is being 
photographed for transcription purposes, the time might arise when it would be 
desirable to go to 35-mm film for the negative, at least in order to get better defi- 
nition. The footnote I should like to add is that at the present time in practice 
the lenses that are being used for this type of work by no means exhaust the reso- 
lution capabilities of the 16-mm film that is being used, and there are lenses avail- 
able commercially at the present time from several manufacturers which would 
permit coming very much closer to the limits of the resolution. That they are 
not placed in service, I presume, is just one of the inevitable examples of tech- 
nological lag that occur when many people are busy doing a job and do not have 
too much time to spend thinking about improving their apparatus. 

With reference to projection lenses, a similar situation exists, on what I believe 
to be reliable information, that in the majority of projectors which are used to 
throw the image on the film into the kinescope for broadcasting, the lens is the 
same lens that normally is supplied in the amateur trade, which is far from ex- 
hausting the detail possibilities of the picture, and here I will be specific. Lenses 
which will do that job are commercially available from at least two reputable 
manufacturers, Bausch and Lomb and Kollmorgen, and the fact that they are not 
put into use for the projectors in the television stations is one of those things that 
requires a little explanation. 

Likewise, with respect to our projection here, I think that it is unfortunate we 
cannot have a lens of that type on the projector used for the Society; however, I 
should like to make this comment about the film that we saw. From long ex- 
perience of the idiosyncrasies of 16-mm films, it looked pretty obvious to me that 
the titles which were spliced into that reel were not on the same stock as the indi- 
vidual scenes, and the curl of the film in the gate was not the same; also that 
the projectionist was focusing on the title, and the picture was actually out of 
focus. It certainly was not doing justice to what was on the film. 

MR. W. H. OFFBNHAUSER: Recently we have seen some advertising of some of 
the newer receivers. The little Hallicrafter 7-inch tube receiver that has a tricky 
type of masking on it is one. I do not know what the rest of it may be, except 
I would rather expect it would limit the picture area to something like 40 or 50 
per cent of the normal standard area. Has there been any trend as far as tele- 
vision receiver production is concerned, to guide that or limit it to meet the sug- 
gestions that have been placed in the SMPE booklet? 

DR. DEANE R. WHITE: It is on the agenda for our committee during the meet- 
ing. The question whether we should take it up has been subjected to some dis- 
cussion by the officers of the Society, because it was not at all certain it was an 
engineering problem as much as it was a commercial problem. I do not know 
what action the Television Committee will take because it is fairly obvious if you 
are going to use them on television and throw them away on peculiar masking 
and receivers, things will not fit, but there are certain commercial aspects of the 
problem entirely separate from the engineering. I would not attempt to predict 
how they would fit into the picture. We can certainly enter into the engineering 
aspect and find out what is wrong and find out what has occurred and whether or 
not we can change them or exchange them. 

MR. PAUL J. LARSEN: I agree with Dr. White to a degree but not completely. 
I believe that it is an engineering organization's responsibility to at least 



126 TELEVISION FORUM DISCUSSION August 

establish standards by which the industry can be guided. As an example, when 
the 16-mm film is in question, we should establish an aperture size that should 
be adopted by the broadcasters, and likewise establish a standard as to what the 
aspect ratio of the picture should be. If someone wishes to change that, then he 
is not abiding by standards adopted. 

MB. R. M. MORRIS: I should just like to throw in for consideration the fact 
that the same problem of aspect ratio exists with respect to our nonrecorded pres- 
entations in broadcasting just as much as it appears in the matter of the presen- 
tation of recorded picture transmission. The aspect ratio of 4 X 3 is set by the 
Federal Communications Commission regulations at the present time, and unless 
it is approached from that standpoint, I do not know that it is a matter especially 
for an SMPE or any other engineering society standardization. It has been con- 
sidered by the Commission, and unless there is good reason to change, I suspect 
that that is one of the things that we can consider fairly well established. 

The matter of masking shape, I think we all considered was more or less well 
established until two or three manufacturers, apparently for commercial reasons, 
chose to try to make the receiving tube more efficient in its utilization of area 
rather than making the system efficient from the utilization of bandwidth, and I 
think it is obviously something which some organization is going to have to make 
recommendations on to the end that there be a standard receiving picture mask 
established. It is a thing in which the broadcasters, of course, are as much inter- 
ested as anyone else. 

MR. EDWARD P. SUTHERLAND: I have seen many motion pictures via tele- 
vision, and it was only recently that I noticed the Lucky Strike series. It is im- 
personal opinion that the picture and sound quality are about the best, and I was 
wondering if Mr. Gudebrod or anyone else here could tell me first of all whether it- 
is a projection print of 35-mm or 16-mm and also what the gamma is. 

MR. GUDEBROD: I am not enough of an engineer to tell you what the gamma is. 
The network is fed by 35-mm print, 16-mm prints being made available for all 
nonconnected stations. 

We have had as I indicated, some considerable argument about the contrast 
range or gamma of the prints which we are using. We have finally prevailed 
upon the producer and some of the engineers on the West Coast to reduce the con- 
trast more in keeping with what we think, by rule of thumb; is right for television 
transmission. About the first six or eight films of the series were pretty harsh. 
We got edge flare. We got halation. We had troubles with it. The later ones 
in the series we think we got pretty well corrected. We have seen them on closed 
circuit, but that, of course, is an ideal situation. It varies considerably when you 
get it actually on the air. 

DR. NORWOOD L. SIMMONS, JR. : I should like to add to Mr. Gudebrod's answer 
regarding the series of productions which were made by Grant-Realm Productions 
for the Lucky Strike show. These pictures were produced in Hollywood and the 
35-mm negatives were developed to a gamma value of 0.65 to 0.70. The 35-mm 
prints were made on regular release positive film, developed to a gamma of about 
2.40, until recently. Then an experimental print was made on fine-grain master 
positive film, developed to a gamma of about 1.40. The printing density used for 
the low-contrast master positives is light, not as would be used for ordinary mo- 
tion picture duplicates, but rather in the nature of those shown by Mi 1 . Bertram 



1949 TELEVISION FORUM DISCUSSION 127 

Mr. Moderator, I should like to ask Mr. Blount if the visual luminosity curve he 
showed was based on equal energies or on tungsten at 3000 degrees Kelvin. 

MR. RICHARD BLOUNT: Equal energies. 

DR. SIMMONS: Is it not then true that the visual-luminosity curve, in order to 
be fairly compared with the product curve of the tube sensitivity multiplied by 
the light-source-output curve, should also be multiplied by the relative output 
curve for the particular light source being considered? 

MR. BLOUNT: In both cases, to be highly accurate we should have used fluores- 
cent lamp or the 3000. I do not feel that for the basis of this presentation that 
degree of accuracy is warranted. 

MODERATOR HYNDMAN: Dr. Simmons, do you not think that there has been 
confusion here this afternoon, with some in the television industry and some in the 
motion picture industry continually talking about controlling contrasts by con- 
trolling gamma, when we think of gamma as applying to a development factor 
only? Literally the problem is, in the majority of motion picture films produced, 
there is a brightness latitude greater than the television system or chain is ca- 
pable of accommodating. For illustration, a latitude brightness range of 1 to 40 
in a motion picture film may be common, and the television system has about 1 to 
20, then television-image distortion of tone occurs regardless of gamma or density. 

DR. SIMMONS: I quite agree with you. I was extremely interested in Mr. Ber- 
tram's samples and should like to congratulate him on an excellent set of tests 
and to tell him that had we had such a set of tests in Hollywood at any time in the 
last six months, it would have straightened out a great many people. I am think- 
ing of the nontechnical people involved in making these films for television, and 
we have tried to straighten them out without the aid of such tests. This was a 
very illuminating test to me. 

I think it is important, though, to point out that, at least as I saw it, the 1.70- 
5302 print appeared less "contrasty" on the screen than the 1.25 fine-grain master 
positive which is because we are dealing with toe portions of the characteristic 
curve. If we consider that the fine-grain master positive has a steeper and 
shorter toe than regular release positive film, then, in consequence, the true con- 
trast of the screen image is not in proportion to the gamma values as read. 

Therefore, it behooves us to consider the curve shape. I may be deviating 
somewhat from your question, but I did want to mention that in Hollywood the 
National Broadcasting Company and others have given thought to that matter 
of curve shape. That is cutting it rather fine possibly, but since there is less toe 
on the fine-grain film, therefore, we have more high-light contrast relative to 
middle tone and high-density contrast. Some people think that helps. Person- 
ally, I do not think the art or science of television has advanced far enough to allow 
us to see any difference yet, and I agree with you, Mr. Hyndman, in saying that 
at the present time the contrast of the print provided is of secondary importance. 

MR. EDMUND A. BERTRAM: To answer Dr. Simmons' question or agreeing 
with him, it is too bad I do not have time to make a slide of the curve character- 
istics, but I do have all the characteristic curves of the particular films shown in 
the 35-mm form. The print at gamma 1.70 is made on a high-contrast film, and 
printed on 5302, developed in negative developer in which we tried to develop a 
shadow density well up on the curve to produce transparencies in the black and at 
the same time bring up the toe. 



Progress Report- 
Theater Television* 

BY BARTON KREUZER 

RCA VICTOR DIVISION, CAMDEN, NEW JERSEY 

Summary In connection with a theater television demonstration of an 
instantaneous theater television projection system, a chronological record 
of the early development and current progress of theater television is pre- 
sented. References are made to both instantaneous projection and the 
kinescope-photography methods. The demonstration consisted of the pro- 
jection by theater television of lantern slides for the paper, live action, and 
film reproduction fed from the anteroom of the auditorium together with 
broadcast television programs received by radio transmission and telephone 
circuits from a near-by television station. 

IT HAS BEEN THE PRACTICE of the Radio Corporation of America 
to report at intervals on the continuing developments in theater 
television. These reports have taken the form of various technical 
papers 1 " 4 of the Society of Motion Picture Engineers, some accom- 
panied by demonstrations, discussions, and demonstration before the 
last two annual conventions 5 - 6 of the Theater Equipment Supply 
Manufacturers Association, a talk at the Televisor Magazine's Tele- 
vision Institute 7 in April, 1948, and a very complete demonstration 
and explanation by Warner Brothers and RCA engineers at the joint 
meeting of the SMPE and the National Association of Broadcasters 
held in the Warner Brothers Studio in May, 1948. This report and 
exhibit of operating theater television equipment is another progress 
report in this series. 

The foundation for this work by RCA goes back a long time, as age 
goes in this new art of television. The first work, started in 1928, 
culminated in a demonstration in January, 1930, in the RKO-58th 
Street Theater in New York City. The system provided a 60-line 
picture with reasonable brightness on an approximately 7 l /y- X 10- 
foot screen, using a rotating-lens disk, Kerr cell, carbon-arc method. 
The need for further work was indicated, about ten years' more! 

This led to the famous 1940 demonstration which some members 
of the SMPE witnessed at the New Yorker Theater in New York. 
(See Fig. 1.) Here a 441-line picture was shown with low brightness. 

* Presented April 4, 1949, at the SMPE Convention in New York. 
128 AUGUST, 1949 JOURNAL OF THE SMPE VOLUME 53 



THEATER TELEVISION 



129 



on a 15- X 20-foot screen using Schmidt-type reflective optics. Fur- 
ther development was interrupted by the war. 

Following the war, the RCA Laboratories reconditioned this same 
system, introduced an improved kinescope, revised circuits to operate 
on the new 525-line standard, and used the equipment in the summer 
of 1946 to show the Louis-Conn fight to an estimated audience of 
3000 on the lawn of the Laboratories in Princeton. 







Fig. 1 Equipment used in New Yorker Theater Demonstration, 1940, 
15- X 20-foot picture. 



1947 provided a 7 l / 2 - X 10-foot television picture demonstration 
both at the TESMA Convention in Washington, D. C., and at the 
SMPE Convention in New York using equipment previously de-' 
scribed. 1 " 4 

In 1948, the demonstrations increased in picture size to 15 X 20 
feet. Demonstrations were made by Warner Brothers in Hollywood 8 
for the SMPE-NAB meeting with equipment described in the same 
papers, 1 " 4 and by Twentieth Century-Fox at the Fox Theater in 
Philadelphia on the occasion of the Louis- Walcott fight. 9 The 
equipment, stripped of its base, was mounted on the front of the 



130 



KREUZER 



August 



balcony. The audience who paid admission that night saw the first 
program to be carried from one city to another on a microwave relay 
system especially for showing in a regular motion picture theater. 
These two demonstrations were both made with reflective optics 




^ijBpB^p^ 



. Fig. 2 Projector with 20-inch mirror and 21-inch plastic lens, demonstrated 
in 1948 at TESMA Convention, St. Louis. 

systems employing 42-inch spherical mirrors, because of their size 
dubbed " Behemoth Mark I." 

In September, 1948, the RCA demonstration of a 15- X 20-foot 
television picture, exhibited to approximately 1200 persons at the 
TESMA Convention in St. Louis, used a smaller equipment with com- 
parable results (Fig. 2). The optics had now been reduced from the 



1949 



THEATER TELEVISION 



131 



500-pound, 42-inch mirror, and its 21-inch glass lens, each of which 
had required months of grinding, to a 20-inch mirror and a 15V2-inch 
plastic molded lens weighing only 50 pounds! 

This equipment, although smaller than previous equipments pro- 
jecting the same size picture, was nevertheless relatively bulky as it 
contained power supply and video amplifiers in the base of the unit. 
Subsequent developments, in addition to improving performance, 
have made it possible to separate the optical barrel from the balance 




THEATRE MOTION 
PICTURE PROJECTOR 



Fig. 3 Schematic of kinescope-photography system. 

of the equipment. Hence, the smaller barrel (30 inches in diameter 
and 36 inches long) is now the only element of equipment required 
in the theater auditorium. It may be mounted from 40 to 65 feet from 
the screen by using appropriate projection lenses, at which distances 
it will project a 15- X 20-foot picture. This particular demonstration 
is limited to 11 X 15 feet by the room dimensions. 

While this development has been taking place the parallel field of 
broadcast television has also developed. Some impression of its 
rapid progress can be drawn from Table I, particularly when it is 
remembered that the average television receiver frequently has more 
than one viewer; literally, an audience running into the millions! 



132 


KREUZER August 
TABLE I 




Cities 


Stations 


Sets 


Eastern network 
Midwest network 
Non-network 

Stations not operating 


8 
. 8 
16 


21 
14 
20 


730,800 
200,600 
152,700 


32 
5 


55 

2* 


1,084,100 
95,900 


37 


57 


1,180,000 



* Now testing; start regular operations in March. 2-26-49 

The discussion thus far has related solely to the instantaneous type 
of television projector. An alternate type of some merit has also 
appeared on the scene, the kinescope-photography system, also called 
the "film-storage" method, or the "intermediate-film" system. In 




* * *** ** .4 



J* 5 3 




Fig. 4 Kinescope-photography system as supplied to Twentieth 
Century-Fox and Warner Brothers. 



1949 



THEATER TELEVISION 



133 



this method, a kinescope television picture is photographed on motion 
picture film, rapidly developed, and, if desired, fed continuously into a 
regular motion picture projector. Diagrammatically, this system 
functions as shown in Fig. 3. Systems of this type, shown in Fig. 4, 
have been supplied to Twentieth Century-Fox and Warner Brothers 
for evaluation of this method. A number of such systems have been 
sold to television broadcasters, not for theater projection use but for 







Fig. 5 TLS-86 projector for use in theater lobbies and lounges, approximately 
7- X 9-foot picture. 



* 'storage" of television programs for later repetition or for syndication 
purposes over other television broadcast stations. These kinescope- 
photography systems are in daily use; very likely many members 
have witnessed film from them on television programs. At the NAB 
Convention early in April, 1949, in Chicago, just such a system 
adapted for broadcast use was demonstrated. 

Theater television programming appears to fall into two broad 
classes: (1) Use of regular television broadcast material; and (2) 






134 KREUZER August 

so-called "closed-circuit" performances in which a privately origi- 
nated program is fed to one or more theaters. 

In the second case, some examples of originating sources might be: 
(A) live action in a studio, from the stage of a theater, or from some 
public gathering such as a sports arena or a political event; and (B) 
motion picture film, either produced in more or less regular fashion, or 
by kinescope photography to "store" some program such as those 
described above. 




Fig. 6 Theater television protector optical barrel mounted near ceiling 
with amplifier system in left foreground. Demonstrated at SMPE Convention, 
Hotel Statler, New York, April, 1949. 

In any case, program transmission might be by microwave relay, 
equalized telephone lines, or by coaxial cable, or some combination of 
these as adequately covered by our own SMPE bulletin on Theater 
Television. 10 

In the theater, such programs can be projected in lounges and small 
auditoriums by commercial equipments such as the RCA TLS-86, 
shown in Fig. 5. For regular theater auditoriums, professional 
equipment will also be available in the near future. RCA expects to 
be in a position to manufacture theater television equipment, based 
upon the prototype system demonstrated at this time, in pilot-run 
quantities possibly by the end of 1949. It is expected that the price 
for a single unit without stand-by facilities would be less than $25,000. 



1949 



THEATER TELEVISION 



135 



ACKNOWLEDGMENT 

Thanks and grateful acknowledgment are due many for the work 
leading up to the demonstration which was presented as part of the 
paper, and for the demonstration itself. Among these are Messrs. 
E. I. Sponable and H. J. Schlafly of Twentieth Century-Fox, Colonel 




Fig. 7 Equipment used in the demonstration at the Hotel Statler ballroom 
with an actual television picture on the screen. The picture originated in an 
anteroom of the ballroom and was fed to the television projector by direct 
cable connection. 

Nathan Levinson and Dr. B. R. Miller of Warner Brothers, Mr. R. D. 
Kell of RCA Laboratories, Messrs. J. E. Volkmann, R. V. Little, 
F. G. Albin, R. C. Wilcox, L. L. Evans, and K. E. Palm of the RCA 
Victor Division of RCA, and Mr. Cy Keen of the RCA Service 
Company. 

NOTE : The demonstration (Figs. 6 and 7) included viewing of the 
lantern slides used by theater television. This was followed by in- 
stantaneous theater television of program material including both 



136 KREUZER 

live action and regular motion pictures. Some of the live action was 
regular program material from NBC television station WNBT of the 
National Broadcasting Company, and the balance was picked up by a 
television camera in the anteroom. The broadcast material was re- 
ceived both through the air by radio transmission and by means of an 
equalized telephone line. The latter is of particular interest since it 
demonstrates one means of intracity transmission, one which does not 
require licenses from the Federal Communications Commission. The 
motion pictures were scanned on equipment also located in the ante- 
room. Both the screen and the film used were supplied through the 
co-operation of Twentieth Century-Fox. The screen was directional, 
of the embossed type, with a brightness gain in excess of 2.0 over that 
using a matte surface. 

REFERENCES 

(1) Ralph V. Little, Jr., "Developments in large-screen television," J. Soc. 
Mot. Pid. Eng., vol. 51, pp. 37-52; July, 1948. 

(2) I. G. Maloff, "Optical problems in large-screen television," /. Soc. Mot. 
Pict. Eng., vol. 51, pp. 30-37; July^ 1948. 

(3) D. W. Epstein and I. G. Maloff, "Projection television," /. Soc. Mot. 
Pict. Eng., vol. 44, pp. 443-455; June, 1945. 

(4) I. G. Maloff and W. A. Tolson, "A resume of the technical aspects of RCA 
theater television," RCA Rev., vol. 6, p. 5; July, 1941. 

(5) TESMA Convention, Washington, D. C., September, 1947. Progress 
Report on Theater Television with Demonstration, J. F. O'Brien, RCA Victor 
Division. 

(6) TESMA Convention, St. Louis, Mo., September, 1948. Progress Report 
on Theater Television with Demonstration, B. Kreuzer, RCA Victor Division. 

(7) Theater Television address by B. Kreuzer before Televisor Magazine's 
Television Institute, April, 1948. 

(8) Progress Report on Theater Television, Nathan Levinson and F. G. Albin 
before May, 1948, meeting of SMPE and NAB at Warner Brothers Studio. 

(9) Roy Wilcox and H. J. Schlafly, "Demonstration of large-screen television 
at Philadelphia," J. Soc. Mot. Pict. Eng., vol. 52, pp. 549-561; May, 1949. 

(10) SMPE bulletin on Theater Television, SMPE Theater Television Com- 
mittee, 1949. Also published in J. Soc. Mot. Pict. Eng., vol. 52, pp. 243-273; 
March, 1949. 

DISCUSSION 

QUESTION: How does the screen brightness here compare with the standard 
set by the Society of Motion Picture Engineers? 

MR. BARTON KREUZER:" Though it is materially improved since the last demon- 
tration, it is still below par. It is at the level of brightness which, unfortunately, 
you still find in many motion picture theaters. 

MR. H. EMERSON YORKE: May I ask when we may reasonably expect large- 
screen television in the theaters? 

MR. KREUZER: Some time toward the very end of this year or early next year. 



Television Pickup for Transparencies 

BY ROGER D. THOMPSON 

ALLEN B. DuMoNT LABORATORIES, PASSAIC, NEW JERSEY 



Summary Scanning an opaque subject or photographic transparency with 
a moving spot of light found application in the early days of television. A 
modern version, using a short-persistence cathode-ray tube as the light 
source, can produce television pictures of excellent quality. Equipment 
restricted to pickup of transparencies can be of simple and reliable design. 
A motor-driven slide-changing mechanism accommodating as many as 
twenty-five 2- by 2-inch glass slides is described. Esthetic transitions 
possible include automatic picture fading preceding and following the slide 
change as well as unblanked changes to give the effect of instantaneous 
change-over. Artistic effects, particularly adapted to the flying-spot device, 
extend its flexibility. 



SINCE THE EARLIEST ATTEMPTS to transmit pictorial information 
between remote points by electrical means, scanning subject 
material with a small spot of light and projecting the transmitted or 
reflected light upon the cathode of a phototube has received atten- 
tion. 1 The first television systems employing this principle utilized 
mechanical methods of scanning. With the advent in 1934 of elec- 
tronic means for producing television pictures, the flying-spot method 
became less popular than the use of the image dissector, the iconoscope, 
and later the orthicon and image orthicon. The competitive position 
of the older scheme has been favored, however, by the recent develop- 
ment of cathode-ray tubes having very short-persistence screens. 
When an electron-multiplier-type phototube is utilized for transla- 
tion, a simple pickup device is possible. 2 

Achieving a pleasing picture by the flying-spot principle in a direct 
pickup of live talent seems difficult when compared to present camera 
practice. The use of photographic transparencies is more convenient 
because the problems of depth of field and intensity of light are greatly 
simplified. 

A practical adaptation suitable for televising 2- by 2-inch glass slides 
is outlined in Fig. 1. A television raster is formed on the face of the 
10-inch cathode-ray tube, which is magnetically focused and 

* Presented April 5, 1949, at the SMPE Convention in New York. 

AUGUST, 1949 JOURNAL OF THE SMPE VOLUME 53 137 



138 



THOMPSON 



August 



deflected. An amplifier is provided for blanking retrace lines to pro- 
duce black reference. Light from the raster is focused by an //1. 9, 
50-mm lens upon a slide and the transmitted light is projected upon 
the cathode of the phototube by a condenser lens composed of two 
plano-convex lenses 2 ! /2 inches in diameter and having focal lengths of 
3y 2 inches. The resulting electron displacement from the cathode 
surface is multiplied by dynode stages of the phototube about 40,000 

PICTURE GENERATOR ^ 



SLIDE CHANGING | 
MECHANISM 



MULTIPLIER TYPE 

PHOTO-ELECTRIC 

CELL 



CONDENSER LENS 



DEFLECTION 
YOKE 




FOCUS COIL 



$. 1 System outline. 



times to produce a signal of 0.2 volt which is applied to the multistage 
amplifier shown in Fig. 2. 

Because of the persistence of the screen of the cathode-ray tube, the 
scanning spot would have a cometlike appearance if it could be viewed 
while in motion. About 0.8 microsecond is required to excite the 
phosphor to 70 per cent of its maximum intensity, and 1.2 micro- 
seconds is required for decay to 30 per cent after the electron beam is 
cut off. Fortunately, both of these effects can be corrected by the 
use of two simple networks, one located in the anode circuit of the 



1949 



TV PICKUP FOR TRANSPARENCIES 



139 



phototube, the other in the plate circuit of one of the amplifier stages. 
An inverter accommodates the use of either a positive or a negative 
slide by reversing the polarity of the video signal. 

A gamma corrector in the form of a remote-cutoff pentode amplifier 
operated with large signal input to cause nonlinearity provides in- 
creased amplification of gray steps near black compared to those near 
white. This transfer characteristic compensates for distortion intro- 
duced by reproducing monitors and receivers. 

To permit adjustment of picture black relative to blanking level in 
the output signal, blanking is emphasized by an inserter stage and 
then clipped at the desired level by a series diode arrangement. A 



IP2I 




5 STAGE 






POLARITY 






GAMMA 


PHOTOTUBE 




AMPLIFIER 






INVERTER 


] 




CORRECTOR 
























SYNC 
INSERTER 







BLACK 
REFERENCE 
CLAMP 






BLANKING 
INSERTER 




















4 


4 


OUTPUT 




f 


AUTOMATIC 


^ 




BLANKING 


OU 1 KU 1 i 

4 


* 


AMPLIFIERS 






FADER 






CLIPPER 



Fig. 2 Block diagram of video circuits. 

clamp on the grid of the gamma corrector sets its proper operating 
point and maintains the blanking level after clipping independent of 
picture content. 

Standard synchronizing signals specified by the Radio Manufac- 
turers Association may be added by an inserter stage. 

The versatility of a scanner for program service can be extended by 
the use of the remotely controlled slide changer shown in the photo- 
graphs of Figs. 3 and 4. A capacitor-type motor is geared through a 
worm reduction to a disk on which a connecting rod is pivoted near the 
rim. A flat plate with a thickness approximately that of a 2- by 2- 
inch glass slide is driven by the connecting rod in a reciprocating 
motion. A slide is positioned between the objective and condenser 
lenses on the forward stroke of the plunger and the next slide to be 



140 



THOMPSON 



August 



used drops into place at the end of the retracting stroke. Thus the 
slides are gravity-fed from the hopper on the left to the slide track, 
are positioned by the plunger, and finally are pushed by the next 




mm 



Fig. 3 Exposed view of slide changer. 







Fig. 4 Slide changer with cover. 

slide into a receiving hopper. The unit shown uses a 3000-revolution- 
per-minute motor, has a 16-to-l reduction system, and completes 
a slide-change cycle in about 0.4 second. The motor picks up speed 
rapidly, and since the beginning of the cycle is chosen well ahead of 
the forward stroke of the plunger, it is operating at full speed during 



1949 TV PICKUP FOR TRANSPARENCIES 141 

the time each slide is positioned. The actual change-over time then 
is less than 0.2 second, and the effect of an instantaneous change-over 
is imparted to a casual viewer. The friction of springs contacting 
the slide being positioned dissipates the momentum imparted to the 
slide. Coasting is further minimized by the sine motion of the 
plunger, which decelerates to zero velocity at the end of the stroke; 
and indexing of the slide is controlled entirely by the dimensions of 
the linkages. A mechanical brake held in contact with a cam raised 
on the rim of the crank disk by spring tension prevents excessive coast- 
ing of the mechanism after the motor is de-energized. The brake is 
released by a solenoid which is wired in parallel with the motor for 
simultaneous operation. A limit switch depressed by cam action at 
the end of the forward stroke completes the cycle. 

To supplement the instantaneous change-over, an automatic con- 
trol circuit has been developed to fade the output video signal of the 
scanner to black, whereupon a slide change is made and a fade-in of 
the next slide follows. Either of two rates of fading can be se- 
lected, and the switch accomplishing the selection, the switch initiat- 
ing the cycle, and all other operating controls can be remotely located. 

An attribute of the flying-spot device is the possibility of attaining 
good geometrical linearity; as little displacement of a point from its 
true position on the raster as 1 per cent of the picture height is pos- 
sible with production units. The evenness of illumination is good. 
Shading is almost entirely due to the optical system and is not objec- 
tionable even when using a negative slide, in which case the gamma 
corrector exaggerates intensity variations. Resolution of 500 lines 
in the horizontal direction, measured by RMA methods, is readily 
attained. Vertical resolution is limited to about 450 lines by the 
number of active scanning lines in the raster. 

The use of color slides for reproduction in black and white is entirely 
feasible and preliminary tests do not reveal adverse effects despite the 
fact that the cathode-ray-tube output and the phototube sensitivity 
are largely confined to the green portion of the spectrum. Because 
of the density of color slides, the signal-to-noise ratio is inferior to 
that obtained by the use of good black-and-white slides. 

Since the raster is sharply focused in the plane of the cathode-ray- 
tube screen, transparencies may be placed on the face of the tube 
with only slight defocusing resulting from the thickness of the glass. 
In this way, two transparencies may be superimposed. An effective 
device utilized by WABD, New York, is that of a special clock made 



142 THOMPSON 

of transparent parts placed upon the face of the tube. Another in- 
novation is the use of a pointer on the face of the tube to attract 
attention to particular portions of the picture. 

There is evidence that cathode-ray-tube scanners will find accept- 
ance for many applications where simplified sources of test and pro- 
gram material are desired. 

ACKNOWLEDGMENT 

Acknowledgment is due the Research Division of the Allen B. 
DuMont Laboratories for development of the cathode-ray tube, to 
Mr. A. J. Baracket for supervision of initial circuit development, and 
to Mr. A. L. Olson for slide-changer and scanning-generator design. 

REFERENCES 

(1) V. K. Zworykin and G. A. Morton, "Television," Section 8.3, John Wiley 
and Sons, New York, N. Y., 1940. 

(2) G. C. Sziklai, R. C. Ballard, and A. C. Schroeder, "Experimental simul- 
taneous color television system, Part II Pickup equipment," Proc. I.R.E., vol. 
35, pp. 862-871; September, 1947. 



FORTY-ONE YEARS AGO 

Atlantic City. Managers of local playhouses will be asked to have a 
hymn sung at each Sunday performance as a compromise with members 
of the local W.C.T.U., which threatened to close the moving picture 
shows given Sunday evenings. 

A special committee of women that visited the shows brought back a 
report that it had discovered nothing objectionable in the performances, 
but recommended that hymns take the place of "illustrated songs," 
with the audience taking part. 

The Moving Picture World, January 25, 1908 



Saloon Men Fight Shows 

Tamaqua, Pa. April 27. The saloon proprietors are now agitating 
against the moving picture shows. These attractions, the saloon 
men say, are taking the crowds from their places of business. 

Throughout this section there is not a town having a population of over 
3000 that does not boast of at least two of these shows, while some have 
as high as four, this town being one of the latter class. All these shows 
are well patronized. Men and boys who would otherwise frequent 
the saloons go there, making the rounds of the shows each evening. 

The saloons in some of the towns are endeavoring to have the shows 
taxed in the same manner as circuses and opera houses. 

Moving Picture World, May 9, 1908 



Use of 35-Mm Ansco Color Film for 
16-Mm Color Release Prints* 

BY REID H. RAY 

REID H. RAY FILM INDUSTRIES, ST. PAUL, MINNESOTA 



Summary In commercial motion picture production, there is often a need 
for both 35-mm and 16-mm color prints. In this field color serves the purpose 
of product identification, and therefore a three-color system is required. 
In the specific work described here, locations were widespread and demanded 
specific dates for shooting. Therefore, several cameramen had to cover 
location assignments almost simultaneously and available 35-mm profes- 
sional photographic equipment had to be used. How both 35-mm and 16-mm 
color release prints were quickly processed from one three-color original is 
described. 



HISTORY OF COLOR in motion pictures, at least up to 1949, can 
J_ be summarized in these 13 words: Kinemacolor, Prismacolor, 
Agfa color, Dufay color, Gaumont color, Technicolor, Cinecolor, 
Multicolor, Gasparcolor, Magnacolor, Kodacolor, Kodachrome, and 
Ansco color, t Perhaps this list may slight some color process, but in 
the main, these names embrace color motion picture history. 

Those of us who have been associated with the production of 
motion pictures for the past 25 years have continually had the "color 
problem" confronting us. Since 1938, when sound Kodachrome 
duplicates were announced, the industrial producer has really become 
color conscious because black-and-white picture production gave way 
to a large percentage of color production, even faster than the pro- 
ducer actually preferred. Color plays a more important role in 
business films than in the theatrical film. The client who pays the bill 
wants the color of his product in motion pictures to be as nearly like 

* Presented February 17, 1949, at the Central Section Meeting, Chicago, 
t It is interesting to note that the first Ansco color 35-mm release won an Academy 
Award. It was a 2-reel short released through Monogram titled, "Climbing the 
Matterhorn" and was shot in 1946 by Irving Allen, while producing a feature pic- 
ture in Switzerland. In 1947, "16 Fathoms Deep" was made in Florida, a 9-reel 
feature in Ansco color, also released by Monogram. A third film, "Alice in 
Wonderland," has just been completed and will be released in 1949, through the 
J. Arthur Rank Organization. In 1948, A & T Productions produced in Paris, 
France, the picture, "The Man on the Eiffel Tower." 

AUGUST, 1949 JOURNAL OF THE SMPE VOLUME 53 143 



144 -RAY August! 

the actual product in real life as possible. While in a theatrical re- 
lease, if the color of the dress of the heroine is a shade or two different | 
from the original, the color director may object but usually the "front I 
office" will remark, "What matters it is still 'color by Technicolor.'" 

When a color production is ordered and only 16-mm prints are re- 
quired, the print job is comparatively simple. Shoot 16-mm com- 
mercial Kodachrome, make 16-mm contact duplicates, and you have 
your best possible release prints. However, when the client asks for i 
35-mm and 16-mm prints in three-color, there has been actually only j 
one process the industrial producer had to turn to, Technicolor. I 
Technicolor production, as everyone knows, is not geared espe- 
cially to industrial production budgets; besides, very often, indus- 
trial location work is complex and camera equipment must be as 
mobile as possible with minimum crews for extensive traveling. This 
paper does not purport that Technicolor does not meet the require- 
ments, but that Technicolor is not an economical color process for 
certain types of industrial color production which this paper presents. 

Of course, two cameras, one 16- and one 35-mm, might be used 
simultaneously on all shots, but this calls for an extra crew, extra equip- 
ment, extra film cost, lighting problems, and double editing, conform- 
ing, and handling all through the production. The purpose of this 
paper is to present a method one production company used to solve 
the request for 35- and 16-mm color release prints and to do it in an 
economical manner. 

The basic 35-mm color film used was Ansco color camera film, 
Type 735, which is an integral subtractive color film of the reversible 
type. Introduced in 1946, this camera film is balanced for exposure 
by daylight and the best color rendition on exteriors is obtained in 
bright sunlight. 1 For interior work, high-intensity arc lamps with 
Y-l filters are recommended for key-lighting with the fill light supplied 
by white-flame arc broads, such as Duarcs, or "CP" lamps filtered 
with MacBeth Whiterlite filters. 

In our studio we have obtained good results with incandescent 
lighting equipment, using CP lamps with MacBeth Whiterlite filters, 
although extremely high total wattage must be used as an exposure 
level of 1000 foot-candles at //2 with color temperature of 5400 
degrees Kelvin is required. That is better understood when one 
knows that the film speed is rated thus: ASA Exposure Index (r. 
Weston, 5; and General Electric, 8. Ansco UV-15 or UV-16 filter or 
the Wratten 114A filter is recommended for all exteriors and interiors. ' 



16-MM ANSCO COLOR PRINTS 145 

Ansco color camera film, Type 735, may be used in regular 35-mm 
professional cameras without any conversion and, therefore, Bell and 
Ho wells, Mitchells, or even Eyemos are satisfactory for production 
work. That fact was very important in the requirement of the indus- 
t rial production job to be described. There were assignments to be 
met within three months' time, scattered from California through 
Colorado, Texas, Kentucky, Mississippi, Illinois, Iowa, Minnesota, 
North Dakota, and Oregon; and half a dozen cameramen, with a 
wide variety of equipment, had to be assigned to shoot the color foot- 
age under a great variety of field conditions. These varied from fly- 
ing over the great wheat fields of the Pacific Northwest with an Eyemo 
in order to climb the steep hillsides to film the harvest ; to standing in 
almost knee-deep water in the rice fields of Mississippi, no place for 
heavy cumbersome color cameras, and the Eyemos and lighter Bell 
and Howells came in handy and turned in creditable color photog- 
raphy. In some locations cameras had to .be secured on top of 
moving machines, and one Mitchell was even tied down inside the 
grain tank atop a huge combine moving over rough ground. 

No photography was planned before 10:00 o'clock in the morning, 
and seldom after 4:30 in the afternoon, and bright sunlight was a 
prerequisite. As a result, a fairly evenly exposed original camera film 
was obtained. Approximately 15,000 feet were shot during those 
three months. It is recommended that one single-emulsion number 
he' used on each production as there is, as in all color processes, some 
color-balance change in succeeding emulsion runs. It was also found 
that pleasing effects and good definition in dark areas were obtained 
with cross, and even partial, backlighting. Naturally extra caution 
was taken in exposure reading and our camera crews carefully con- 
sidered the subject before deciding on a lens stop. 

After the original camera film was exposed, it was shipped to the 
Houston Color Laboratories in West Los Angeles for developing and 
printing a "daily." During the past 10 months this laboratory has 
been processing approximately a half -million feet per month of Ansco 
color film, and is equipped to turn out a daily print within 48 hours. 
The processing of Type 735 camera film is almost identical to a 
description by Forrest, 2 except for a somewhat shorter developing 
time in both the first developer and the color developer. 

In making a daily print from the original camera film, each scene is 
not timed for density and color balance, but an over-all average printer 
exposure and an average filter balance are determined and the daily is 






146 RAY August 

printed. The printing stock is Ansco color release film, Type 732, 
also a reversible-type film of relatively low speed, very fine grain, and 
special sensitization for printing. 3 

When the daily print is received, it is edited as in black-and-white 
production, and the track is recorded. This step is followed by re- 
recording sound effects and musical background. At this point a 
word should be given about the type of track best suited for Ansco 
release printing. Excellent results with no loss in reproduction 
volume have been obtained using the direct-positive method of final 
recording. A studio recorder, Radio Corporation of America PR 23, 
was converted to handle either negative or direct-positive recording. 
Otherwise in negative sound recording, with a positive track furnished 
for printing, some method has to be devised to realign the track place- 
ment because the track must be on the opposite side of the film for 
printing a reversible type of color system. 

Conformation of the original camera film with the edited daily work 
print follows and lap dissolves or other effects may be inserted as 
there is Ansco color Type 132 duplicating film and Ansco color Type 
154 masking film available for making effects on optical printers. 
When conformation is complete and the re-recorded direct-positive 
film is synchronized, this material is delivered to the laboratory to 
prepare a composite print. In timing the original, the laboratory now 
times each scene for printing, as in black-and-white procedure, except 
that each frame of the timing strip has a different filter balance and 
there are several density balances made on each scene. 4 From these 
strips, a timing number and a filter combination are selected to print 
each scene. The first print from the assembled negative, known as 
the answer print, has scene-for-scene density and color correction. 
The Bell and Howell printers used have been remodeled to provide a 
light source of 3200 degrees Kelvin for printing the Ansco color release 
positive, Type 732, and for inserting filters into the light source quickly 
and for the rapid changing of these filters during printing. This answer 
print is shipped to the producer for approval and if color balance on 
certain scenes needs changing, a second answer print is processed. 
After an approval has been obtained, release prints are ordered and 
the 35-mm print requirements are supplied. 

MAKING THE 16-MM COLOR PRINT 

Each 35-mm release print is carefully inspected, and one is selected 
to be used as the master for the production of the 16-mm release prints 



1949 16-Mn ANSCO COLOR PRINTS 147 

by optical reduction to Kodachrome. The original camera film, Type 
735, which is being used for 35-mm printing cannot be used inasmuch 
as available reduction printing equipment is not equipped to make 
filter changes scene by scene. However, the 35-mm release print is 
color-balanced scene for scene and, therefore, it can be used as the 
master for the 16-mm reduction printing. The 35-mm print is first 
carefully timed, although very few light changes are needed, and 
with the proper filter pack, customarily used in printing Kodachrome 
duplicates, a 16-mm reduction print is made. A Depue reduction 
printer, using a 250-watt lamp, with a blower added to dissipate the 
heat for filter protection, is used for this work. Although the print 
being used for the picture reduction work is a composite print with 
track, this track is not used for sound printing. A 35-mm direct- 
positive variable-area track with additional compression for 16-mm 
reproduction was recorded for this assembly immediately after the 
re-recorded track was made for the 35-mm prints. An RCA 35- to 
16-mm optical reduction sound printer, running 180 feet per minute, 
prints the sound on the 16-mm Kodachrome print stock. 

Although the resulting 16-mm Kodachrome release print is a 
second-generation print, it is quite acceptable, and compares favor- 
ably with 16-mm Kodachrome contact duplicates from 16-mm Koda- 
chrome originals. This is, no doubt, due to the fact that the original 
was shot on 35-mm film and that a reduction print results in better 
quality than a 16-mm contact print. 

Approximately fifty 16-mm reduction prints each of two 2-reel 
pictures were made by this method, and the 35-mm Ansco release print 
used did not show any noticeable scratches, shrinkage, or warpage 
from its runs through the Depue printer. Both 35- and 16-mm prints 
were released within three weeks after the day the last scene was 
photographed an excellent record for fast service, and credit is due 
the two laboratory crews who helped make such a record possible. 

In the production of commercial motion pictures, problems of loca- 
tion work, economy of operation, making the best of conditions as 
they are found in the field, and transportation of photographic equip- 
ment have a direct bearing on the increased use of business films. 
Therefore, a practical solution in producing commercial films in 35- 
and 16-mm color has been desired for a number of years. Al- 
though the method just described of how 35-mm Ansco professional 
color film Type 735 was used to produce 35- and 16-mm release prints 
may be improved in the future, the method still did make possible an 



148 RAY 

acceptable color process, with distinct production advantages, to a 
large user of commercial films. It is the belief of the author that the 
"difficult can be done immediately; the impossible takes a little 
longer." An answer to the difficult was found; perhaps the "impos- 
sible" will be solved in the years ahead of us. 

REFERENCES 

(1) H. H. Duerr and H. C. Harsh, "Ansco color for professional motion pic- 
tures," /. Soc. Mot. Pict. Eng., vol. 46, pp. 357-368; May, 1946. 

(2) J. L. Forrest, "Machine processing of 16-mm Ansco color film," /. Soc. 
Mot. Pict. Eng., vol. 45, pp. 313-327; November, 1945. 

(3) Garland C. Misener, "Notes on the use of Ansco color camera film Type 
735," Motion Picture Division, Ansco Company, Binghamton, N. Y., 1949. 

(4) Data furnished by Robt. F. Burns, Laboratory Manager, The Houston 
Color Laboratories, West Los Angeles, Calif., 1949. 



"The Motion Picture Theater, 
Planning and Upkeep" is a proud 
presentation of the SMPE, based on 
a project directed by James Frank, 
Jr., who also has written the Fore- 
word. The book is attractively bound 
with a hard cover of green buckram. 
There are 428 pages, generously 
illustrated and distinctively designed 
with modern typography. 

This book was planned by a group 
of leading architects, engineers, and 
theater-circuit executives responsible 
for construction and maintenance. 
They felt that many theater owners 
now planning new construction or 
modernization had need for latest 
authentic information on the subject. 
They also felt that the Society of 
Motion Picture Engineers could and 
\v;is obligated to supply this informa- 
tion. Therefore, a wealth of data on numerous phases of theater design, con- 
struction/ and'upkeep has been assembled under eight major headings. 

The book is available at $5.00 per copy. Add 2 per cent sales tax for 
New York City deliveries. Price per copy, postage*prepaid, outside the con- 
tinental United States, $5.50. 

SOCIETY OF MOTION PICTURE ENGINEERS 
342 Madison Avenue, New York 17, N. Y. 




Direct- Positive Variable-Area 
Recording with the Light Valve* 

BY LEWIS B. BROWDER 

WESTERN ELECTRIC COMPANY, HOLLYWOOD, CALIFORNIA 



Summary By reflecting light from the back surface of the light-valve 
ribbons and focusing the ribbon edges at the film plane a bilateral or uni- 
lateral type of direct-positive variable-area track is obtained. By relocat- 
ing the recording lamp so that light is transmitted through the space between 
the ribbons a normal variable-area negative may be obtained. 



ANEW FILM RECORDING MACHINE designated as Type RA-1231 
was described in the JOURNAL 1 in 1946 employing the tight-loop, 
controlled -compliance type of film drive. As shown, the recorder was 
equipped with a small, variable-density type of modulator. Since 
then, there have been described a 200-mil push-pull density modu- 
lator 2 and a light- valve-type, double-width, push-pull variable-area 
modulator 3 both of which operate with the same basic film-pulling 
unit as was shown with the small modulator. In this paper is de- 
scribed the fourth in the series of modulators for use in the Type RA- 
1231 recorder; i.e., a simple, compact, standard variable-area modu- 
lator. As in the other modulators, the ribbon light valve is employed 
as the basic modulating element, the field of application of this device 
being extended in this modulator to the recording of direct-positive 
variable-area sound track as well as the standard negative variable- 
area track. 

The direct-positive recording facility is of particular interest in 
connection with those black-and-white and color processes in which 
the composite prints are obtained by photographic reversal from 
positive sound track and picture films. 4 - 6 The direct-positive sound 
track thus eliminates the intermediate sound print which ordinarily 
would be required with such processes. The direct-positive sound 
track also holds promise in certain television applications where the 
tonal scale on the television screen is reversed electrically to give a 
positive picture on the film. 

* Presented October 26, 1948, at the SMPE Convention in Washington. 

AUGUST, 1949 JOURNAL OF THE SMPE VOLUME 53 149 



150 BROWDER August 

PRINCIPLE OF DIRECT-POSITIVE RECORDING 

For recording direct positive, the aperture between the light-valve 
ribbons must be projected on the film as a dark area so that it will 
develop out to clear film. The aperture image must, of course, be 
bounded by an exposed area which will develop out black on the film. 
Thus as the ribbon aperture is made smaller in response to noise- 
reduction bias, the percentage of clear area in the developed track be- 




Fig. 1 Basic optical system for direct-positive recording. 

comes less and the ground noise in the reproduced film is corre- 
spondingly reduced. In principle, this reversal of clear and exposed 
area from the situation obtained with the standard negative recording 
system is accomplished as follows : 

As shown in Fig. 1, the light valve is equipped with a high-quality 
apochromatic objective lens. Light from the recording lamp is 
directed off the inclined slit mirror into this objective lens, the working 
distances being such that an image of the lamp filament is formed at 
the plane of the light-valve ribbons. As in previous light valves, the 
width of the ribbon is considerably larger than the thickness. This 



1949 DmECT-PosiTivE RECORDING 151 

thin, flat ribbon is suspended in the fixed magnetic field so that electri- 
al currents flowing lengthwise through the ribbon will cause it to move 

ewise in the plane of the flat surface. For this light valve, the foil 

m which the ribbon is to be sheared is polished optically smooth and 
iven a mirror-quality surface finish. When stretched between the 
bbon clamp carriages, the ribbon appears as a thin strip mirror whose 
surface is perpendicular to both the optical axis and the axis of the 
lamp-filament image. The width of this strip mirror is defined by the 
accurately straight edges of the ribbon and is much less in extent than 
the length of the spatial image of the lamp filament, with the result 
that the actual area of illumination of the ribbons remains constant 
as the ribbons are modulated. There is thus formed by the polished 
ribbon surface a mirrored image of just that portion of the filament 
image which it intercepts. 

Since the ribbon moves laterally across the filament image in re- 
sponse to modulation currents it, in effect, scans the image directing 
the reflected light back toward the light-valve objective lens. By 
means of optical expedients to be described later, the individual coils 
of the image of the lamp filament are made to blend with one another 
so that the filament appears as a uniformly illuminated rectangle of 
light. Thus each reflected element of the image appears identical to 
any other differing only in lateral position as determined by the in- 
stantaneous displacement of the light-valve ribbon. 

Two of these reflecting ribbons are employed in this light valve 
They are arranged side by side and accurately adjusted so that their 
reflecting surfaces are coplanar. These ribbons may be connected to 
record either a bilateral or a unilateral type of variable-area sound 
track. 6 In the unilateral case one of the ribbons is connected to move 
in response to noise-reduction currents while the other moves in re- 
sponse to speech currents. As seen from the light-valve objective 
lens there appear two brightly illuminated patches, the inner edges 
of which move in response to speech and noise-reduction currents 
to define the lateral extent of the embraced dark area. This situation 
when projected onto the film is correct for the recording of direct- 
positive variable-area sound track. The inclined mirror by which 
the light from the recording lamp is directed into the light-valve ob- 
jective lens contains a narrow, rectangular, clear slit extending across 
its width through which the light can pass to the film. 

As shown in Fig. 1, the light proceeds from the recording lamp to the 
inclined slit mirror which directs all but that lost through the slit 



152 



BROWDER 



August 



upward to the light-valve objective lens. This lens forms a spatial 
image of the lamp filament at the plane of the light-valve ribbons. 
The reflecting surfaces of the ribbons in turn form virtual images of 
sections of the filament image, which virtual images are limited in 
extent by the width of the ribbons and are located also at the ribbon 
plane. The light-valve objective lens then picks up these reflected 
images and reprojects them, this time through the clear slit in the 
inclined mirror and to the film. The cylindrical lens located near the 



POSITION OF LAMP FOR RECORDING 
'VARIABLE AREA NEGATIVE SOUND TRACK 



RECORDING LAMP IN ' 
POSITION FOR DIRECT 
POSITIVE RECORDING 



LIGHT TUNNEL 1 CONDENSER LENS 
USED FOR NEGATIVE RECORDING 



REFLECTING SURFACE OF 
LIGHT VALVE RIBBON 




CONDENSER LENS FOR 
DIRECT POSITIVE RECORDING 



^RECORDING IMAGE 



PARTIALLY REFLECTING GLASS HERE 
REFLECTS FRACTION OF RECORDING 
BEAM BACK TO PHOTOCELL FOR PEC 
MONITORING OR FORWARD TO EYEPIECE 
FOR VISUAL MONITORING 



Fig. 2 Optical system schematic of variable-area modulator. 

film gathers the beam of light from the slit and converges it to the 
narrow line required for the recording image. 

OPTICAL SYSTEM 

The complete optical system of this modulator is depicted sche- 
matically in Fig. 2. The recording lamp is of the pref ocused type rated 
at 5 amperes and 10 volts having a single-helix, curved, horizontal 
filament. The axis of the filament is rotated at 45 degrees to the 
optical axis which has the effect of reducing the pitch of the filament 
helix to the point where there are no dark spaces between the coils 
and the whole length of the filament appears uniformly bright. Some 
gain in optical efficiency and a considerable saving in space is achieved 
by locating the lamp fairly close to the light valve employing an 
auxiliary lens to throw a virtual image of the lamp filament back to the 



1949 DIRECT-POSITIVE RECORDING 153 

proper distance for projection by the light-valve objective lens to the 
ribbon plane. In order to maintain the recording lamp in its normal 
vertical operating position the light valve is located immediately 

Ee the slit mirror with the light-valve objective lens facing down- 
. The slit mirror is a front-surface, aluminized, glass mirror with 
a,r slit across its width. The width of this slit together with the 
reduction afforded by the objective cylinder lens determines the 
height of the recording image. The clear slit in the mirror casts a 
shadow which disappears at the ribbon plane but reappears in the 
reflected beam from the ribbons in such a way that the slit ordinarily 
would be in its own shadow and no light would be available for re- 
cording. By displacing the slit from the optical axis through slightly 
more than half its width, the shadow is thrown to the opposite side of 
the optical axis making the full-intensity beam available for recording. 
The mounting of the apochromatic objective follows previous practice 
in that it is located within the light-valve structure. Since the light 
valve is intended to be a readily replaceable component, this arrange- 
ment confines any slight, mechanical misregistration of the light valve 
with its mounting to the image space of the objective lens where such 
displacements are not subject to optical magnification. 

The reflected light from the ribbon passes through the clear slit to a 
front-surfaced plane mirror whose function is to turn the recording 
beam through 90 degrees to a horizontal axis. The objective cylinder 
lens is located near the film and is adjusted to focus an image of the 
clear slit in the above mirror onto the emulsion of the recording film. 
Separation of the cylinder lens into two components is resorted to as 
shown in order to minimize the cylindrical equivalent of spherical 
aberration. 

Recording of a standard negative track is accomplished by bringing 
the light in through the edge of the light valve as shown in Fig. 2. 
Upon reaching the optical centerline of the valve, the beam is de- 
flected downward by a prism to the condenser lens. An image of the 
lamp filament is focused by the condenser lens slightly beyond the 
ribbon plane in order to minimize the effects of the filament stria tions 
further. The rear-illuminated aperture between the ribbons is then 
projected by the light-valve objective lens through the slit and to the 
film. As in the direct-positive setup, the cylinder lenses focus the slit 
onto the film emulsion to define the height of the recording image. 

Light for phototube monitoring is obtained from the horizontal 
section of the recording beam by a thin, inclined, clear-glass wafer 



154 



BROWDER 



August 



which subtracts a fraction of the beam by Fresnel reflection directing 
it back to the monitoring phototube. In the viewer a similarly 
located but oppositely inclined mirror throws the reflected fraction of 
the recording beam forward allowing the spatial image of the light- 
valve ribbons to be inspected wih a microscope eyepiece. 

THE LIGHT VALVE 

The folded-magnet structure employed in previous variable-area 
light valves 3 is used here, as are the beryllium-copper ribbon clamp 
carriages with their adjustments for ribbon spacing, height, and tuning 




ZOO 500 1000 

FREQUENCY IN CYCLES PER SECOND 

Fig. 3 Frequency response of light valves. 

tension. A box-shaped Alnico magnet comprises the main body of the 
case with Permendur pole-pieces closing the ends and carrying the 
magnetic flux to the center of the valve where the ribbon gap is 
located. One of these pole-pieces supports the objective lens as well 
as the clamp carriages while the other contains the condenser lens and 
the prism arrangement by which light is directed to the ribbons for 
negative recording. 

The surface quality of the light-valve ribbons used for direct-posi- 
tive recording must, of course, be quite good. Of the several ma- 
terials suitable for use in the fabrication of the light-valve ribbon, 
aluminum offers'definite advantages from the standpoint of electrical 
performance 7 although unfortunately it? softness presents some 



1949 DIRECT-POSITIVE RECORDING 155 

problems in the achievement of a satisfactory surface finish. However, 
by careful maintenance of the rolls with which the foil is worked, ex- 
cellent foil surfaces have been obtained comparable in reflectance to 
an aluminized mirror. 

The relationship between the amplitude of ribbon displacement 
and applied voltage at the a 600-ohm primary of the light-valve match- 
ing coil is shown in Fig. 3. The somewhat higher peak exhibited by 
the bilateral light valve is due to the use of a series resistor in the 
Simplex noise-reduction circuit with which this valve is used. The 
light valve looks back into a circuit of relatively high impedance so 
that the effectiveness of the electromagnetic damping is somewhat 




Fig. 4 Square-wave response of light valve. 

reduced. The unilateral valve, on the other hand, looks back directly 
into the low-impedance secondary of the matching transformer with a 
consequent improvement in the electromagnetic damping characteris- 
tic. Fig. 4 shows an oscillogram of the monitoring phototube output 
as the unilateral valve is driven through its matching transformer 
with a square-wave generator having a fundamental frequency of 800 
cycles per second As used in a recording system, the resonant peaks 
are usually flattened by means of a light-valve equalizer which im- 
proves the square-wave response also. 

MECHANICAL ARRANGEMENT OF THE MODULATOR 

The only mechanical difference in the setup for recording negative 

track and that for recording direct positive is in the manner in which 

the light from the recording lamp is conducted into the light valve. 

By mounting the recording lamp on a movable slide, it becomes 



156 



BROWDER 



August 



possible to effect this change merely by moving the recording lamp from 
one position to the other. Fig. 5 is a photograph of the modulator 
with the light valve in place and the lamp moved up to the position 
for recording negative sound track. Fig. 6, in which the modulator is 
mounted in its recorder, shows the lamp moved down in position to 
record direct-positive sound track. The lamp bracket is mounted in a 
dovetail slide equipped with adjustable stops at each end of its travel. 
After the stops have been adjusted and locked for a particular lamp, 
the transition from direct-positive to negative recording may be 

accomplished in a matter of 
seconds merely by moving the 
lamp. 

The light valve is a completely 
self-contained component of the 
modulator, the mounting being 
arranged so that it may be re- 
moved readily from the modula- 
tor proper for inspection or re- 
placement. Registry of the face 
of the light valve with the modu- 
lator mounting plate is accom- 
plished by constructing this plate 
of soft steel so that the leakage 
magnetic flux from the valve 
serves to hold the valve face 
tightly against this plate. A 
single milled slot in the valve face 
and a dowel in the mounting 

Fig. 5-Modulator and light valve. P Me loCate the Valve in the 

right and left directions while 

registry tabs at the back of the mounting plate bear against the rear 
edge of the valve to locate it fore and aft. After the valve is pushed 
home against the registry tabs, a clamping lever is swung into 
place and tightened to augment the magnetic clamping force further. 
Release of this lever then^ allows the valve to be slid across the steel 
mounting plate and finally lifted clear. 

The objective cylinder lenses are mounted in a cylindrical cell 
which is spring-loaded against a threaded ring. Calibrations on the 
periphery of this ring serve as a reference in making film tests to estab- 
lish the optimal focus setting. Provision is made for a limited range 




DIRECT-POSITIVE RECORDING 157 

of adjustment of this cell about its longitudinal axis for setting the 
azimuth of the recording image to the precision required in variable- 
area recording. 

The monitoring facilities are designed as self-contained accessories 
which may be installed into the modulator in place of the right-hand 
small circular cover seen in Fig. 5. The phototube monitoring attach- 
ment is an assembly of deflecting glass and a field lens for producing a 
variable-intensity spot on the plate of the phototube. This assembly 




Fig. 6 Modulator and light valve in recorder. 

and the chassis containing the monitoring phototube and amplifier 
constitute the complete phototube monitoring unit. The visual 
monitoring accessory consists of a microscope eyepiece with its 
mounting for installation into the modulator. A graduated scale is 
located in the focal plane of this eyepiece which enables the setting of 
the noise-reduction current to obtain a given width of bias line. 

PERFORMANCE 

Both the unilateral and the bilateral light valves require an input 
level of +20 dbm* into the primary of the matching transformer for 
operation to 100 per cent modulation. This figure applies, of course, 
for either direct-positive or negative operation. 
* Decibels with respect to 0.001 watt. 



158 



BROWDER 



For direct playback of the direct-positive track, maximum cancella- 
tion of the cross-modulation products is obtained by exposing EK- 
1372 or EK-5372 variable-area film to a total density 8 of 1.3. A fre- 
quency film recorded at constant modulation of the light valve and 
exposed to this optimal density exhibits a frequency characteristic as 
shown in Fig. 7 for both the 35-mm modulator and the 16-mm version 
which uses a narrower recording slit to improve the frequency response. 



+ 5 

8 



16 MILLIMETER 



200 SOO 1000 2000 

FREQUENCY IN CYCLES PER SECOND 



K>000 20000 



Fig. 7 Frequency response of direct-positive film. 

REFERENCES 

(1) G. R. Crane and H. A. Manley, "A simplified all-purpose film recording 
machine," /. Soc. Mot. Pict. Eng., vol. 46, pp. 465-475; June, 1946. 

(2) J. G. Frayne, T. B. Cunningham, and V. Pagliarulo, "An improved 200-mil 
push-pull density modulator," /. Soc. Mot. Pict. Eng., vol. 47, pp. 494-519; 
December, 1946. 

(3) Lewis B. Browder, "A variable-area light-valve modulator," /. Soc. Mot. 
Pict. Eng., vol. 51, pp. 521-534; November, 1948. 

(4) G. C. Misener and G. Lewin, "An application of direct-positive sound 
track in 16-mm release processing by duplication method," J. Soc. Mot. Pict. Eng., 
vol. 46, pp. 167-168; March, 1946. 

(5) "Recent American standards for 16-mm and 8-mm emulsion position," 
/. Soc. Mot. Pict. Eng., vol. 49, pp. 547-558; December, 1947. 

(6) John G. Frayne, "Variable-area recording with the light-valve," J. Soc. 
Mot. Pict. Eng., vol. 51, pp." 501-521; November, 1948. 

(7) T. E. Shea, W. Herriot, and W. R. Goehner, "The principles of the light 
valve," J. Soc. Mot. Pict. Eng., vol. 18, pp. 697-732; June, 1932. 

(8) Dorothy O'Dea, "Comparison of variable-area sound recording films," 
J. Soc. Mot. Pict. Eng., vol. 45, pp. 1-10; July, 1945. 



35-Mm and 16-Mm Portable 
Sound- Recording System* 

BY E. W. TEMPLIN 

ELECTRICAL RESEARCH PRODUCTS, HOLLYWOOD 38, CALIFORNIA 



Summary A new low-cost portable sound-recording system suitable for re- 
cording a standard variable-density sound track on 35-mm or 16-mm film in 
synchronism with a motion picture film is described. The basic system in- 
cludes a two-channel mixer, a main amplifier including associated noise-re- 
duction circuits, a compact recorder, and a power unit for operating the 
entire system from a 115-volt, alternating-current supply. An optional 
inverter providing for operation from 96-volt batteries and an alternating- 
and direct-current multiduty motor-control unit are also available. The vari- 
ous circuit facilities and the performance of the components and system 
with respect to sensitivity, signal-to-noise ratio, harmonic distortion, and 
flutter are discussed in detail. The mechanical and electrical design of the 
equipment make possible a high-quality sound product for both speech and 
music recordings, the performance specifications being consistent with the 
requirements and standards of major Hollywood studios. 



GENERAL DESCRIPTION 

ANEW LOW-COST lightweight portable sound-recording system 
suitable for recording a standard variable-density sound track on 
35-mm or 16-mm film in synchronism with a motion picture film is 
now available in the Western Electric 300 Type recording system. 
The assembled system, as shown in Fig. 1, consists of three electronic 
units, a mixer, amplifier, and power unit, each assembled in an 
attractive duralumin case, plus a compact recording machine also well 
adapted for portable application. 

Although limitations on weight and size are imposed by the porta- 
bility requirements, the equipment retains a frequency-response 
range and freedom from distortion consistent with the high-quality 
requirements of major studio production. In addition, variable 
equalization facilities are incorporated for controlling the frequency re- 
sponse in the low-, medium-, and high-frequency ranges to obtain the 
best possible sound product for either speech or music recordings on 
both 16-mm and 35-mm film, and for the wide range of pickup con- 
litions found in the studio and on location. 

Presented April 24, 1947, at the SMPE Convention in Chicago. 

AUGUST, 1949 JOURNAL OF THE SMPE VOLUME 53 159 



160 



TEMPLIN 



August 



The electronic components operate from a single-phase 50- to 60- 
cycle, 115-volt power source with a total drain of less than 2 amperes. 
The recording machine motor may be either a 3-phase, 220-volt syn- 
chronous type, a conventional 3-phase alternating-current interlock, or 
a 96-volt direct-current multiduty motor, depending on the type of 
power source provided for driving the motors of the associated 
cameras. Alternatively, by means of a supplementary electronic 
inverter, shown dotted in Fig. 1, the entire system, including the re- 
corder and camera motor, may be operated from 96-volt batteries. 

Five 6-conductor-shielded cables terminating in Cannon type "P" 
connectors are required for connecting the components together. Ad- 



OPTIONAL ACCESSORIES. 

RA-1278 PEC MONITOR 
HA-I289A SLATED 
R A- 1290* PUNCH 




Fig. 1 Basic 300 Type recording system block schematic. 

ditional cables are required for the microphones and for connection to 
the power source. Six varieties of the "P"-type connectors are used in 
order to minimize the possibility of mispatching cables. The assign- 
ment of terminals on the connectors has been arranged to prevent 
damage to components in the event cables are accidentally connected 
to the wrong receptacle. 

The microphone cables normally are 100 feet long. The system will 
also accommodate a 100-foot separation between mixer and amplifier. 
The amplifier, recorder, and power unit are intended to be located 
close together so that all may be under the operating control of the 
recordist. The power-supply cable may be as long as necessary, pro- 
viding the terminal voltage at the power-supply input is within the 
range of 100 to 130 volts. 



1949 



PORTABLE RECORDING SYSTEM 



161 




I 



162 TEMPLIN August 

MIXER 

The RA-1283 mixer is shown schematically in Fig. 2. Two micro- 
phone inputs are provided, working into separate preamplifiers. 
These amplifiers are arranged to operate from microphones having a 
30-ohm impedance such as the Western Electric RA-1142 (cardioid) 
type. The preamplifiers have a gain of 33 decibels, an overload level 
of dbm* for 1 per cent total harmonic distortion, and a background 
noise level of 93 dbm at the amplifier output. 

Separate variable dialog equalizers are provided in each preamplifier. 
This feature is desirable not only to provide greater flexibility but be- 
cause of special requirements in a low-cost system that it be possible to 
use the original film for release negative rather than undergo a costly 
re-recording process. In applications of this type, background music 
might be recorded simultaneously with the picture and the low- 
frequency equalization for the music would generally be considerably 
less than for the dialog. As another example, in a two-microphone 
setup where acoustics differ markedly in the two positions, the 
equalizers may be adjusted so that they are balanced in the original 
recording, thus eliminating the necessity of frequency-response re- 
adjustment during a subsequent re-recording process. 

The desired equalization characteristic is obtained by series and 
shunt elements in the plate circuits of the preamplifiers. The rela- 
tively high impedance of the plate circuit allows a smaller space and 
weight for the components than would be possible in the 600-ohm 
output circuit. The dialog-equalization characteristics are described 
in detail in a later portion of this paper. 

Separate mixer potentiometers follow the preamplifiers. These are 
standard 600-ohm bridged-T type having l 1 /^ decibel per step ( 3 /4 
decibel per step when bridging two contacts) and tapered to full cutoff 
at the maximum counterclockwise position. The mixer potentiome- 
ters terminate in a combining network, the output of which is carried 
to the mixer output terminals. 

Either phototube or direct monitoring may be selected by the 
mixer operator providing the optional RA-1278 phototube monitor 
assembly is installed in the recorder. 

A volume-indicator, direct-monitor line is bridged from the main 
amplifier output. The volume-indicator circuit includes a high- 
speed meter and a control switch providing a range from +2 to +24 

* Decibels with respect to 0.001 watt. 



1949 PORTABLE RECORDING SYSTEM 163 

dbm for 0-decibel meter deflection. Direct-monitor level for the 
mixer operator is adjustable by means of a bridged-T continuously 
variable attenuator which provides a level from 10 dbm to cutoff for 
100 per cent modulation of the light valve. An auxiliary direct- 
monitor circuit, at a fixed level of 18 dbm for 100 per cent light- 
valve modulation, is provided for the microphone-boom operator. 

The RA-1283 mixer requires 0.6 ampere at 8.3 volts direct current 
for the vacuum-tube heaters and the volume-indicator meter lamp, and 
5 milliamperes at 220 volts direct current for the plate supply. 

A front view of the mixer, with cover removed, is shown in Fig. 3. 
The mixer potentiometer and dialog equalizer for one microphone 
channel are on the left and for the other on the right. In the central 




Fig. 3 RA-1283 mixer front view. 

portion, below the volume-indicator meter, from left to right, are the 
phototube, direct switch, volume-indicator range switch, and monitor 
volume control. 

A rear view of the mixer is shown in Fig. 4. On the left side is the 
mixer monitor jack. On the rear are receptacles for two microphone 
cables, low- and high-level interconnecting cables to the R A- 1282 
amplifier, and auxiliary monitor. 

The cover, not shown in the photographs, can also be latched to the 
under side of the mixer when the equipment is in use, thus avoiding 
the possibility of its being left behind as the mixer is moved about from 
one setup position to another. The mixer is 15 3 /4 inches long by 6 
inches high by 8 l /z inches deep, including cover, and weighs 1 7 J /2 pounds. 



164 TEMPLIN August 

AMPLIFIER 

The RA-1282 amplifier is shown schematically in Fig. 5. This unit 
contains the main system amplifier, a 1000-cycle test oscillator, vari- 
able low-, middle-, and high-frequency equalization, a noise-reduction 
circuit for automatically biasing down the light-valve spacing in 
accordance with the envelope of the modulating signal, a volume-indi- 
cator circuit, and the recorder lamp-control circuit. 

The amplifier section is a 3-stage unit having either 60, 70, or 80 
decibels gain. By connecting an internal strap the gain may be in- 
creased 5 decibels on each of the above steps. The power output is 
+ 18 dbm for 1 per cent total harmonic distortion and +22 dbm for 5 




Fig. 4 RA-1283 mixer rear view. 

per cent total harmonic distortion. A maximum output of approxi- 
mately +25 dbm prevents damage to the light valve under conditions 
of excessively high input signals. The background noise level at the 
amplifier output with the mixer turned OFF is 56 dbm on low gain, 
51 dbm on medium gain, and 41 dbm on high gain. Under 
normal operating conditions the signal-to-noise ratio of the amplifier is 
65 decibels or well above that of the mixer preamplifiers. 

The first stage of the amplifier uses a 403-B or -C vacuum tube con- 
nected as a pentode with cathode feedback. The feedback may be re- 
duced by installing the short-circuiting strap mentioned above to 
raise the amplifier gain by 5 decibels. This strap is located con- 
veniently on the subpanel on the top side of the main chassis. The 



1949 



PORTABLE RECORDING SYSTEM 



165 




166 TEMPLIN August 

first stage of gain is resistance-capacitance-coupled to the second 
stage, the latter having a grid pot for controlling the gain in three 10- 
decibel steps. This control is located on the front panel. 

The second and third stages utilize a 403-B or -C and 6AK6 Type 
vacuum tube, respectively, with feedback around the two stages from 
plate to cathode. 

A high-pass filter, located at the input to the first stage provides 
optimum low-frequency cutoff for either 16-mm or 35-mm recording 
or may be switched out of the circuit. An inductance-capacitance 
resonant circuit in the cathode of the second stage provides adjustable 
mid-frequency equalization. High-frequency equalization is located 
in the 600-ohm output circuit of the amplifier. These will be described 
in detail later. 

The test oscillator is used to check continuity, to determine light- 
valve overload level, to set noise reduction, and otherwise align the 
system. It uses a 6AS6 vacuum tube in a modified Transitron circuit. 
A Western Electric 400A germanium crystal is used in the cathode 
circuit of this tube, its steep resistance-versus-current characteristic 
acting to stabilize the oscillator. The oscillator frequency is approxi- 
mately 1000 cycles per second and its output level sufficient to over- 
load the light valve on medium-gain step. Continuously variable 
oscillator output control is provided. The oscillator heater is paral- 
leled with those of the other tubes so that the test tone is available 
immediately when the oscillator OFF-ON switch supplies plate voltage 
to the oscillator. The noise-reduction circuit comprises three tubes 
used as audio amplifier and rectifier, carrier oscillator-modulator, 
and modulated-carrier power amplifier, respectively. 

The first stage uses a 6AQ6 duo-diode-triode. The triode section 
amplifies the signal input, which is bridged from the main amplifier 
output. An input potentiometer serves as a noise-reduction margin 
control. An isolating resistance between the amplifier output and the 
noise-reduction input allows the latter to be short-circuited without 
affecting the main amplifier output when the light-valve switch is in 
the OFF position. This prevents noise-reduction signals from modu- 
lating the valve when unmodulated biased and unbiased test tracks 
are being made at the end of a take. The duo-diode portion of the 
tube serves to rectify the signal. This is then filtered to provide a 
varying direct current proportional to the envelope of the input signal. 
The attack and release times of the noise-reduction system are also 
established by the elements of this filter. 






PORTABLE RECORDING SYSTEM 



167 



In the second stage is a 6AS6 tube operating in a 30-kilocycle 
Hartley oscillator circuit, with suppressor-grid modulation obtained 
from the signal envelope described above. 

The output amplifier stage uses a 6AK6 vacuum tube. A grid 
potentiometer provides a control of the bias current and thus controls 
the amount of noise reduction being applied to the light valve. The 
output is transformer-coupled to a full-wave copper-oxide rectifier 
which is filtered to provide a modulated direct current varying in- 
versely with the envelope of the signal. 

A volume-indicator meter and range switch similar to that provided 



TE.R AND &ANGE CONTROL 




EOUC1 



MONSTOR 



VALVE. 



Fig. 6 RA-1282 amplifier front view. 

in the mixer and a lamp-current control circuit are also included in 
this unit. The lamp-current meter may alternatively be switched to 
read the value of noise-reduction bias current. 

A front view of the amplifier is shown in Fig. 6. In the upper left 
are the amplifier-gain switch and oscillator-gain potentiometer. Below 
these are the oscillator OFF-ON switch and lamp operate-hold switch. 
The left-hand meter indicates lamp or noise-reduction-bias current as 
selected by the switch in the lower center. The lamp-current rheostat 
is located below the associated meter. The right-hand meter is the 
volume indicator with the volume-indicator range switch located im- 
mediately below. In the upper right are the noise-reduction input 






168 



TEMPLIN 



August 



(or margin) and noise-reduction bias-control pots. Below them are 
the noise-reduction and light-valve OFF-ON switches. 

Three receptacles are provided on both the left and right ends for 
interconnection cables to the associated units, one of the recorder 
cables being required only when the optional phototube amplifier is 
installed in the recorder. A monitor jack for the recordist is also 
located on the right side. When the top cover is in place, the side 
flaps are held closed over the receptacles, thus protecting them from 
dirt and physical damage. 



TERMINALS A- A & S-8 TOP, STRA 
M!6H FREQUENCY SGBJWLiZATW !N 



MiD-fRSOUENCt 
EQUALIZATION 

CONTROL 




Fig. 7 RA-1282 amplifier chassis top view. 

By loosening two screws on each end of the unit, which are located 
on the interconnecting-cable receptacle panels, the chassis may be 
slipped from its case. A top view of the chassis with cover removed is 
shown in Fig. 7. 

The high-pass filter (or low-frequency equalization) control switch 
is shown on the subpanel at the extreme left. In the center portion of 
the subpanel the mid-range and high-frequency equalization controls 
are located. By replacing strap A-A with strap B-B the high-fre- 
quency equalization may be removed completely from the circuit. The 
RA-1282 amplifier is 15 ! /2 inches long by Il 3 /s inches high by 9 inches 
deep and weighs approximately 32 pounds. 



1949 



PORTABLE RECORDING SYSTEM 



169 




00 
ab 



170 TEMPLIN August 

POWER UNIT 

The R A- 1284 power unit provides plate and heater voltages for all 
vacuum tubes and 12 volts direct current for the recorder exciter 
lamp. The power unit operates from a single-phase, 50 to 60-cycle 
power source of 100 to 130 volts. Taps on the input transformer pro- 
vide for a power supply nominally 105, 115, or 125 volts. 

A schematic of the unit is shown in Fig. 8. A power-supply switch 
controls power to the complete system. The 12-volt, direct-current 
portion of the unit utilizes a bridge-type selenium rectifier and induct- 
ance-capacitance filter. This circuit supplies 4.5 amperes to the 



RECEPTACLE FOR 
POWER INPUT 
r CABLE 




RECEPTACLES FOR 
INTERCONNECTING 
CABLES TO 
AMPLIFIER 



Fig. 9 R A- 1284 power unit front view. 

recorder exciter lamp and 0.3 ampere each to the heaters of the two 
mixer preamplifiers and the first amplifier stage in the main amplifier. 
These three heaters are fed through separate ballast lamps which 
regulate the current to the required value independent of power- 
supply voltage, variations in lamp current, and length of connecting 
cables between the amplifier and the mixer.. The remaining tubes in 
the RA-1282 amplifier receive heater supply from a 6.3-volt, alternat- 
ing-current transformer in the power unit. The center- tap of the 
winding receives a 6-volt bias from resistances R8 and R9, which re- 
duces to a negligible value the introduction of hum components from 
the heaters. 

The plate-supply circuit provides 30 milliamperes regulated at 180 



1949 



PORTABLE RECORDING SYSTEM 



171 



volts for the main amplifier and 15 milliamperes unregulated at 
approximately 275 volts for the mixture preamplifiers and the op- 
tional phototube monitor unit. Regulation of the 180-volt circuit is 
provided by the two gas tubes V2 and VS. The 275-volt supply is 
filtered further in the amplifier to provide 5 milliamperes at 220 volts 
direct current at the mixer terminals. 

A small fan provides forced-draft cooling for the unit, drawing cool 
air in past the selenium-rectifier plates and forcing the air out past the 
other components. The use of the forced draft allows a considerable 
saving in weight and space for the rectifier and still allows a reasonable 
safety factor in the event of failure of the ventilating system. 




Fig. 10 RA-1284 power. unit chassis bottom view. 

Fig. 9 shows a front view of the power unit with the top cover re- 
moved. The air intake for the cooling system is in the center, with 
the exhaust on the two sides. Also shown on the front panel are the 
power switch, power input and plate-supply fuses, and a power pilot 
lamp. Receptacles for the two interconnecting cables to the amplifier 
unit are shown on the right. A power-input receptacle is similarly 
located on the left side. Side flaps protect the receptacles when the 
cover is installed, as already described for the RA-1282 amplifier. A 
bottom view of the chassis with the cover removed is shown in Fig. 10. 
This shows an adjustable resistor on the right for setting the lamp 
current within the desired -range, an adjustable resistor on the left for 
setting the regulating range of the gas tubes (depending on whether or 



172 TEMPLIN August 

not the optional phototube monitor assembly is used), and in the 
center, the adjustable taps for 105, 115, or 125 volts supply voltage. 
The power unit is mounted in a case the same size and of the same 
appearance as already described for the R A- 1282 amplifier. The 
weight is 38 pounds. 

In order that the system may be operated entirely from 96-volt 
batteries, an auxiliary inverter unit has been developed. It supplies 
60-cycle power at a nominal 115 volts to the RA-1284 power unit, the 
total battery drain under full load being approximately 2.3 amperes. 
This unit contains a vibrator and associated tapped autotransformer 




Fig. 11 RA-1231 Type recorder. 

which permits adjustment of output voltages to 115 volts 5 per cent 
for battery-supply voltages in the range of 85 to 105 volts. The unit 
is compactly constructed for portable operation, its dimensions being 
approximately 8 X 9*/2 X 15 ! /2 inches and its weight 40 pounds. 

RECORDER 

The recording machine, previously described in the JOURNAL/ may 
be either the RA-1231 or RA-1231-A Type, depending on whether 35- 
mm or 16-mm film is being used. The 35-mm model is shown in Figs. 
11 and 12. A conversion-part set allows the recording machine to be 
modified at the studio or in the field so that it may be used inter- 
changeably with the two widths of film. This recorder includes a 
sealed light valve and simplified modulator with prefocused lamp, 
producing a standard 100-mil variable-density track for 35-mm re- 
cording or standard 80-mil variable-density track for 16-mm recording. 



1949 



PORTABLE RECORDING SYSTEM 



173 



A new fluid damped drive mechanism, also described in the JOUR- 
NAL, 2 is utilized. With this drive the 96-cycle flutter is essentially 
negligible and the total flutter for all frequency bands from two to 200 
cycles per second is approximately 0.05 per cent. The total weight of 
the recorder, less film magazine, is 76 pounds. Standard Mitchell 35- 
mm and 16-mm magazines have been adapted for use with this re- 
corder. A transformer, matching the 600-ohm output of the amplifier 
to the light valve, and a noise-reduction Simplex circuit are provided 
in the recorder. 

The optional RA-1278 phototube monitor assembly, when pro- 
vided, is also mounted in the recording machine. The amplifier por- 




*; 






Fig. 12 RA-1231 Type recorder front interior view. 

tion of this assembly is shown schematically in Fig. 13. It is a two- 
stage unit with feedback around the first stage. One 1620 and one 
6J5 vacuum tube are used. The output impedance of the amplifier is 
50 ohms to match the mixer monitor circuit. It provides an output 
level of 10 to +8 dbm, depending on the type of light valve and lamp 
current used. For conditions of extremely low input-signal level the 
gain may be increased 10 decibels by means of a strap on the terminal 
strip which reduces the feedback. The total harmonic distortion at 
maximum operating level is not over 1 per cent. The signal-to-noise 
ratio with 100 per cent light-valve modulation is over 45 decibels. A 
continuously variable output attenuator is provided for balancing the 
output against the direct monitor level. A 600-ohm test input is 



174 



TEMPLIN 



August 




Fig. 13 RA-1278 phototube monitor unit schematic. 

provided on the phototube socket for making electrical transmission 
tests. The amplifier chassis is flexibly mounted to prevent micro- 
phonic noise when the recorder is operating. 

As shown in Fig. 14 the phototube monitor assembly includes a de- 
flector subassembly and a relay lens in addition to the amplifier 
chassis. The deflector transmits approximately 10 per cent of the 
incident modulated light through an aperture and the relay lens to a 
phototube mounted on the amplifier chassis. This chassis is located in 
the rear compartment of the recorder. 

Several types of driving motors are available. These, with their 
associated chain and sprocket kits permit alternative operation syn- 
chronously from a 50- or 60-cycle, 3-phase supply, in interlock from a 




ASO-39965 
AMPLIFIER 




' SHOCK MOUNTING BASE 

Fig. 14 RA-1278 phototube monitor unit assembly. 



L949 



PORTABLE RECORDING SYSTEM 



175 



3-phase distributor system, or in a multiduty motor system energized 
from a 3-phase, 220-volt alternating-current line or 96-volt batteries. 
For multiduty motor operation an optional R A- 1444 control unit has 
been developed. This unit provides means for controlling one recorder 
motor and two camera motors when operating from either an alter- 
nating- or direct-current power source. When working from a 3-phase 
alternating-current supply all motors operate synchronously. When 
operating from batteries they may be operated individually or in inter- 
lock at film speeds of 21 to 25 frames per second for both 16-mm and 
35-mm film. 




ZOO 500 1000 2000 

FREQUENCY IN CYCLES PER SECOND 



Fig. 15 RA-1283 mixer dialog-equalizer characteristics. 

An RA-1289-A photographic slater and RA-1290-A film punch are 
available as accessory items. These mount within the recorder and 
are energized from the RA-1284 power unit. 

RESPONSE CHARACTERISTICS 

The over-all frequency-response characteristic of the system without 
equalization is essentially flat from 50 to 10,000 cycles per second with 
the amplifier on each of its gain settings. However, in actual practice 
the characteristic is always modified to achieve particular over-all 
effects as discussed below. 

Fig. 15 shows the frequency-response characteristic of the RA-1283 
mixer, using the various steps of dialog equalization contained in each 



176 



TEMPLIN 



August 



mixer preamplifier. The setting used in any particular instance will 
depend on the acoustic conditions on the set, the presence of wind or 
other low-frequency noises, and the quality of the particular voice being 
recorded. 3 These equalizers are adjustable in 5 steps of 4 decibels each 
at 80 cycles per second with an OFF position. The shape of the family 
of curves agrees closely with those in general use in Hollywood 
studios. The average setting is 4 or 8 decibels for 35-mm recording 
and 12 or 16 decibels for 16-mm recording. For music recording the 
dialog equalizer is normally in the OFF position. 

Fig. 16 shows the frequency-response characteristic for the high- 




-5 
-10 

-15 

"~ -20 















^ 









, - - 


: : -- 


























// 


































17 


































7 


96 MM 




















9 *2S 










/ 






















y 


16 MM 


9.* 










/ 


I , 




























/ 


> 


























I 








I 


/ 


































/ 




























t 






































































9 


O 


rOO 200 500 


KXXD 20OO 5OOO K/OOO 2OOOO 



FREQUENCY IN CYCLES PER SECOND 

Fig. 16 High-pass filter characteristics. 

pass filter which is located at the input of the R A- 1282 amplifier. 
The high-pass filter is used particularly to eliminate components be- 
low the fundamental dialog frequency such as are produced by 
resonance effects on the set or other extraneous noise sources. These 
unwanted components, which may be subaudible, are thereb}'' pre- 
vented from operating the noise-reduction circuit or intermodulating 
the audible signals. The filter cuts off rather sharply, with the 6- 
decibel loss point at approximately 120 cycles per second for 35-mm 
recording, and 180 cycles per second for 16-mm recording. A switch 
located on the upper side of the amplifier chassis transfers between 
these two positions or removes the filter from the circuit. 

It will be observed that the dialog equalizer and high-pass filter 



1949 



PORTABLE RECORDING SYSTEM 



177 



combine to produce the desired over-all response at the low-frequency 
end, and that the low-frequency loss from each of these networks is 
greater for 16-mm than for 35-mm recording. This is because the 
high-frequency cutoff point is at a lower frequency in the 16-mm 
application because of the reduced film speed and it is necessary to 
reduce correspondingly the low-frequency response to obtain the most 
pleasing over-all balance. 

Fig. 17 shows the adjustable mid-frequency equalization character- 
istics. The mid-frequency equalization requirements are based on ex- 
perimental listening tests which have shown that the "presence" in 
dialog recording is made more realistic by accentuating the response 



RELATIVE RESPONSE IN db 

+ + 
o w 5 




















































































16 MM 

1 
























\ 
















STEP 

1 


5 


3 


5M 


M) \ 


\ 






















STEP 4 (35 MM ) * 
STEP 3 (35 MM) 


\\\ 






















STEP 2 (35MM) N 
STEP 1 (35MM) \ 


s 


\~ 


^ 




























[^^^ 




^ 


^ 















































































































































































200 500 1000 2000 

FREQUENCY IN CYCLES PER SECOND 



Fig. 17 Mid-range-equalizer characteristics, 
in this range. The amount of this equalization varies somewhat in 
different studios and also depends on the type of microphone used, 
some of which have at least one resonant peak in this portion of the 
spectrum. With the Western Electric RA-1142 microphone a 3- 
decibel boost at 3000 cycles is an average equalization value for 35- 
mm recording. For 16-mm recording, additional pre-emphasis peaking 
at approximately 5000 cycles is added to the "presence" equalization 
in view of the inherent cutoff at 4500 to 5000 cycles on the reproduced 
film. Five steps of equalization of 1 decibel each plus an OFF position 
are available for 35-mm recording and one position for 16-mm record- 
ing. This control is also located on the upper side of the amplifier 
chassis. 



178 



TEMPLIN 



August 



Fig. 18 shows the frequency-response characteristic for the high- 
frequency equalization . For 35-mm recording this consists of an equal- 
izer having response complementary to the resonance characteristic 
of the light valve, thereby making the light- valve modulation corre- 
spond to that of the signal over the entire useful frequency range. This 
characteristic introduces a loss of 9 decibels at the light-valve resonant 
frequency of 9000 cycles. For 16-mm recording this equalizer is 
switched to provide a low-pass filter cutting out slightly above 5000 




20 



too 



5000 IOOOO 20000 



200 500 1000 2000 
FREQUENCY IN CYCLES PER SECOND 

Fig. 18 Light-valve equalizer and low-pass filter characteristics. 

cycles in order to suppress those frequency components beyond the 
16-mm useful range. 

OVER-ALL SYSTEM CHARACTERISTICS 

Typical over-all-electrical-response characteristics for recording on 
35-mm film are shown in Fig. 19. For dialog recording the low fre- 
quencies are attenuated and the mid-range boosted to obain the most 
realistic dialog quality. The light-valve equalizer is used to comple- 
ment the effect of light-valve resonance. For music the low-frequency 
and mid-frequency equalization are removed. The light- valve 
equalizer is left in the circuit to provide an over-all system response 
(up to the film) which is flat over the useful frequency range, thereby 
obtaining the maximum fidelity for the recorded music. 

In Fig. 20 a typical over-all electrical response for 16-mm recording 
is shown. As previously described, for dialog recording the 1<>\\ 



1949 



PORTABLE RECORDING SYSTEM 



179 



frequencies are attenuated to a greater extent than for 35-mm recording 
to obtain the proper balance with the high frequencies which are cut 
off at 5000 cycles. The mid-range boost and pre-emphasis are also 
shown. For music recording the low frequencies are attenuated to a 
lesser extent than for dialog. However, the extreme low frequencies 
are eliminated and the mid-frequency emphasis is retained to give the 
most desirable over-all response. Fig. 21 shows a transmission sche- 
matic and level diagram of the complete system for normal conditions 
of operation. Vertical lines on the chart represent fixed gains or losses. 
Sloping lines represent variable gains or losses. 




-30 



DIALOGUE 



20 



100 



IOOO IOOOO 2O 000 

FREQUENCY IN CYCLES PER SECOND 

Fig. 19 35-mm recording over-all-electrical-response characteristics. 

Starting at the microphone, at the left end of the chart, an input 
level of 70 dbm is assumed. This corresponds approximately to 
that obtained from a Western Electric RA-1142 microphone located 3 
feet from an average dialog source. 

The signal level at the preamplifier outputs under these conditions 
is 37 decibels below their overload point, thus allowing an adequate 
margin for extremely high-level signals. 

For this input signal level of 70 dbm the normal mixer output 
level of 55 dbm is obtained with 12 decibels attenuation remaining 
in the mixer pots. The signal-to-noise ratio at the mixer output under 
these conditions is 56 decibels. 

For the normal mixer output level of 55 dbm, a +15 dbm level 



180 



TEMPLIN 



August 



is obtained at the output of the final amplifier stage on medium 
amplifier gain step. This level corresponds to 100 per cent modulation 
of an average RA-1241 Type light valve. The amplifier signal-to- 
noise ratio of 65 decibels is well above that of the mixer unit. The 
signal-to-noise ratio of the system for this average recording condition 
is 55 decibels at the output of the electrical circuits. An effective 
signal-to-noise ratio of approximately 48 decibels can be realized from 
35-mm film, and approximately 46 decibels from 16-mm film, with the 
application of noise reduction as provided in the system. 

The system in normal operation has a margin of 3 decibels between 




100 1000 

FREQUENCY IN CYCLES PER SECOND 



10000 



20000 



Fig. 20 16-mm recording over-all-electrical-response characteristics. 

the overload point of the light valve and the level at which the ampli- 
fier distortion reaches 1 per cent. Peak signals which are allowed to 
overload the valve for increased effective signal level can extend 7 
decibels beyond the light-valve overload point with not over 5 per cent 
distortion. For peak signals 2 decibels below light-valve overload, and 
under optimum film-processing conditions, intermodulation can be | 
held to 6 per cent, corresponding to approximately 1.5 per cent total 
harmonic distortion. 

Fig. 22 shows typical frequency-response characteristics obtained ; 
from a 35-mm and 16-mm print for constant modulation of the light j 
valve. The high-frequency losses include all film losses introduced 
in the recording and printing processes. They do not include i 



1949 



PORTABLE RECORDING SYSTEM 



181 



8 2 I s g 




ii 






bC 





182 



TEMPLIN 



reproducing scanning losses since the data were obtained by scanning 
the print with a microdensitometer. 

CONCLUSION 

It is felt that the compactness, sturdy construction, and portability 
features of this equipment amply meet the requirements of the in- 
dustry for a sound-recording system for general location work. Its 
versatility and flexibility of operation are of particular value to the 
small studio which from the standpoint of economy and convenience 
finds it extremely advantageous to have one type of system meet its 





*' 




UJ 

> -10 



-zo 



to 



50 



16 MM 



100 



tOOOO 20000 



200 500 1000 2000 5< 

FREQUENCY IN CYCLES PER SECOND 

Fig. 22 Response characteristics from film print with constant light-valve 

modulation. 

needs for dialog and music recording on 16-mm or 35-mm film, in the 
studio or on location. As indicated from the performance character- 
istics described in this paper, the mechanical and electrical design of 
the equipment make possible a high-quality sound product, the specifi- 
cations for frequency range, signal-to-noise ratio, harmonic distor- 
tion, and flutter content being consistent with current requirements of 
major Hollywood studios. 

REFERENCES 

(1) G. R. Crane and H, A. Manley, "A simplified all-purpose film recording 
machine," /. Soc. Mot. Pict. Eng., vol. 46, pp. 465-475; June, 1946. 

(2) C. C. Davis, "An improved film-drive filter mechanism," /. Soc. Mot. 
Pict. Eng., vol. 46, pp. 454-465; June, 1946. 

(3) D. P. Loye and K. F. Morgan, "Sound picture recording and reproducing 
characteristics," J. Soc. Mot. Pict. Eng., vol. 32, pp. 631-348; June, 1939. 



Demineralization of Photographic 
Wash Water by Ion Exchange* 

BY HARRY P. GREGOR AND N. N. SHERMAN 
POLYTECHNIC INSTITUTE OF BROOKLYN, BROOKLYN, NEW YORK 



SummaryAn ion exchange system has been developed to purify photo- 
graphic wash water and allow its re-use. The effluent from a print-washing 
machine is cycled through a cation and then an anion exchange resin bed, 
and returned to the machine. The purity of the water obtained approaches 
that of distilled water. 

This unit was developed for the United States Signal Corps, to be used 
in mobile photographic units, and is designed to reduce the amount of water 
required for print-washing. This process is applicable not only to circum- 
stances where water is scarce, but also to processes where wash-water 
purity and temperature control are important, as in color photography. 



THE ION EXCHANGE PROCESS 

CATION EXCHANGE RESINS are insoluble, high molecular weight 
poly acids. They are prepared either by treatment of formed 
resins to produce acidic groups in the structure, or by having one of 
the substances used in the resin synthesis already contain the acidic 
group. An example of a cation exchange resin is shown in Fig. 1, 
where the resin has been prepared using phenol and formaldehyde 
(the normal constituents of Bakelite-type resins) and phenolsulfonic 
acid. 

Cation exchange resins contain either phenolic, carboxyl, or sulfonic 
acid groups. Phenolic groups dissociate only in strongly alkaline 
solutions. Carboxyl groups dissociate at pR values above 7 to 8, while 
sulfonic acid groups are completely dissociated at virtually all pH. 
values. The identification and chemical reactivity of these types of 
exchange resins are described by Gregor and Bregman. 1 

In a dissociated acidic group, the hydrogen ion is held in the im- 
mediate vicinity of the fixed anionic group by electrical forces, for the 
system must be electrically neutral. The hydrogen ion can, however, 
be displaced from the resin if another cation diffuses into the structure 
to take its place. Thus, if a solution of sodium chloride is placed in 

* Presented October 28, 1948, at the SMPE Convention in Washington. 

AUGUST, 1949 JOURNAL OF THE SMPE VOLUME 53 183 



184 



GREGOB AND SHERMAN 



Augustl 



contact with the resin, the sodium ions replace the hydrogen ions and i 
the solution is converted into one of hydrochloric acid. The sodium I 
ion, in turn, can be displaced by other cations, including hydrogen. 
The reaction may be written, where the subscript R refers to the resin I 

phases: 

(R S0 3 - -H+) R + Na + -+ (R S0 3 - -Na + ) R + H + 

The extent of exchange is governed by a modified mass-action effect. 
Anions present in the solution take part in this reaction only to the 
extent to which they determine the pH. For example, sodium ions 



O.H 



OH 



CH 2 - 



CH a 




OH 



CATION EXCHANGE RESIN 

PHENOLSULFON 1C -PHENOL -FORMALDEHYDE 
Fig. 1 

can be taken up by phenolic groups only from a strong base solution, 
such as sodium hydroxide. Here the action of the resin is technically 
that of base absorption rather than cation exchange. This is also 
true for carboxyl resins, at lower pR values. If a solution of sodium 
chloride is passed through a bed of carboxyl resin exchanger, a small 
amount of sodium ions are exchanged, and then the hydrochloric 
acid formed represses the ionization of carboxyl groups and inhibits 
further exchange processes. The nature of the anion has no effect 
where sulfonic acid resins are used. 

Anion exchange resins are insoluble, high molecular weight poly- 
bases, usually of the nitrogen-base type. Their active groups are 
either of the amine type, which is weakly basic, or may be of the 



1949 DEMINERALIZATION OF WASH WATER 185 

guanidine or quaternary type, which are strongly basic. A weak-base 
resin prepared from aniline and formaldehyde is shown in Fig. 2. 

The action of an anion exchange resin depends upon its base strength 
in exactly the same manner as that of a cation exchange resin is 
controlled by its acid strength. A weak-base resin can act only in 
acid solutions, where it absorbs acids through the formation of a salt. 
This is demonstrated also in Fig. 2. Thus, if a solution of sodium 
chloride is passed through the resin, practically no reaction occurs. 
However, if that solution were first passed through a cation bed in the 
hydrogen state and converted to hydrochloric acid, the acid could be 
absorbed and thus all of the salt removed, a process known as 
demineralization. 



:H 2 NH 








CH 5 - NH 







CH, 




ANION EXCHANGE RESIN 
ANILINE FORMALDEHYDE 
Fig. 2 



eak-base anion exchange resins usually will absorb only those 
ids having an ionization constant of 10~ 7 or larger. Thus, boric 
acid (Ka = 6 X 10 ~ 10 ) is not absorbed from solution. Strong-base 
anion exchange resins are completely ionized at virtually all values of 
pR and thus, if originally in the hydroxide state, can convert a sodium 
chloride solution into sodium hydroxide. Very weak acids, which 
are not absorbed by weak-base exchangers, can be absorbed by the 
strong-base resins. Some typical reactions are: 

(R NH 2 ) R -f Na + + Cl- -* No Reaction 

(R 4 N+OH-) R + Na+ + Cl~ (R 4 N + -C1-) R + Na + + OH 

(R NH 2 ) R + H+ + Cl- -* (R NH.+ C|-) R . 



186 



GREGOR AND SHERMAN 



August 



The exchange capacities of commercially available ion exchange 
resins vary from 2 to 10 milliequivalents per gram of dry resin; most 
resins have capacities in the range 3 to 6 milliequivalents per gram. 
Ion exchange resins are manufactured in mesh sizes ranging from 
16 to +50 United States Sieve, and are usually hard granules hav- 
ing negligible solubility. 

EXPERIMENTAL PROCEDURES 

Laboratory ion exchange beds were prepared to a depth of 6 inches 
in 1-inch plastic tubes. The details of the construction and opera- 




Fig. 3 

tion of such tubes are described in handbooks published by the vari- 
ous ion exchange resin manufacturers. Because of the small size of 
these beds, slow flow rates of the order of 5 to 10 milliliters per minute 
were used. Cation exchange resins were put in the hydrogen state 
with hydrochloric acid, anion exchange resins in the base state with 
sodium hydroxide. 

Two kinds of experiments were carried out, one with single beds 
and slow rates of flow, another with a cation and an anion exchange 
bed connected in series (for demineralization), operating at a high 
rate of flow with recirculation. A diagram of this latter apparatus is 
shown in Fig. 3. The purity of wash water was measured by elec- 
trical conductance. Provision was made for other measurements, 



1949 DEMINERALIZATION OP WASH WATER 187 

including pH, rate of flow, pressure loss across beds, and chemical 
analysis from specific parts of the system. 

Original experiments were performed using a natural used fix solu- 
tion (Kodak F-5), which contained 1.55 milligrams of silver per 
milliliter. A synthetic used fix was prepared by allowing 2.5 gram 
AgN0 3 , 1.8 gram KBr, and 0.1 gram KI to react in solution, filtering 
off the precipitate, and dissolving it in one liter of fresh fix solution 
(Kodak F-5) . Four milliliters of developer (Kodak-76) were added to 
simulate natural conditions. This synthetic used fix solution con- 
tained 1.36 milligrams of silver per milliliter and was found to be stable 
for some weeks. 

To simulate actual conditions which exist in print-washing, the 
synthetic used fix solution was diluted 1 : 100 before being passed 
through the beds for the slow runs. The actual performance of the 
resins and their capacities were quite independent of the dilution 
ratio, within wide limits. With the fast runs involving recircula- 
tion, the synthetic used fix was added directly to the washing tank, so 
that the volume of water in the system was constant. 

Standard analytical procedures as described in SMPE publications, 
particularly that of Atkinson and Shaner, 2 were used. 

EXPERIMENTAL RESULTS 

The chemistry of the ion exchange process for the demineralization 
of photographic wash water depends in part upon the rate of flow in 
the system. At slow rates of flow, the sodium salts are converted to 
the corresponding acids by passage through the cation exchange bed. 
The principal constituent of the fixing bath, sodium thiosulfate, is 
converted to thiosulfuric acid. Since this acid is unstable, it decom- 
poses to form colloidal sulfur and sulfite. This process occurs both 
in the cation bed and in the effluent. 

The silver complex breaks down due to the destruction of thiosul- 
fate, and the silver ions react to form silver sulfide. No silver is 
taken up by the cation exchange bed under these circumstances. 
Other cations as potassium and aluminum are exchanged in the bed. 
The reactions are : 

2(R S0 3 --H+) R + Na 2 S 2 O 3 -* 2(R SO 3 --Na + )+H 2 SO 3 + S 
2Ag(S 2 3 ) 2 - -* 2Ag+ + 4(S 2 3 ) -> Ag 2 S 2 O 3 + 3S 2 3 

Ag 2 S 2 O 3 + H 2 O -* Ag 2 S + H 2 SO 4 . 

Silver sulfide appears as a black precipitate. It settles out with the 
colloidal sulfur, or if the cation effluent is passed directly into an 



188 GREGOR AND SHERMAN August 

anion exchange bed, a layer of silver sulfide and sulfur is deposited on 
top of the latter bed. While the silver ions liberated by the decom- 
position of the complex might be taken up directly by the cation resin, 
the successive passage of more thiosulfate solution through the bed 
will reform the complex. In no cases was silver found in the cation 
bed. 

The anion exchange bed was found to have absorbed thiosulfuric, 
sulfuric, and sulfurous acids. The ratio of thiosulfate to sulfite was 
usually rather small, and depended upon the rate of decomposition of 
the former into the latter. Acetic acid was absorbed, although boric 
acid remained in solution except when a strong-base anion exchange 
resin was used. 

When the synthetic used fix was added to runs where water was 
recirculated at a rapid rate through the demineralization system, de- 
composition of thiosulfate and the appearance of colloidal sulfur were 
not observed. This is because the decomposition takes place at a 
finite rate, and the thiosulfuric acid is absorbed in the salt state, i.e., 
neutralized, before it can decompose. It was found that even at high 
rates of flow, the resins used absorbed the synthetic used fix as fast as 
it entered the beds. The rate-determining step for the process was 
that determined by the volume of the tank and the rate of flow, i.e., 
the rate* of dilution. 

Several different resins were tested for this process. It was found 
that Dowex 50* was the most satisfactory cation exchanger, being 
able to convert 1.5 liters of synthetic used fix solution per liter of bed. 
lonac A 300 f was found to be the most efficient anion exchange resin 
for this process, absorbing the cation effluent from 800 milliliters of 
synthetic used fix per liter of resin bed. Since this resin has approxi- 
mately 20 per cent of its capacity in the form of strong-base groups, it 
also absorbs boric acid. 

When a demineralization run was carried out with the volumes in 
the two beds adjusted for equivalent capacity, an over-all capacity of 
500 milliliters of synthetic used fix solution is absorbed per liter of 
total bed volume. The results of a typical run are shown in Fig. 4. 
Here the capacity of the cation bed has been made larger than that of 
the anion bed. The conductance of the cation effluent is larger than 
that of the influent because of the exchange of sodium ions for faster 
moving hydrogen ions. The anion effluent has a specific conductance 

* Dow Chemical Co., Midland, Michigan. 

t American Cyanamid Co., New York, New York. 



1949 



DEMINERALIZATION OF WASH WATER 



189 



of 1.2 X 10 ~ 5 mho, has a pH of 6 to 7, and approaches distilled water 
in purity. In Fig. 4, the acid-absorbent capacity of the anion bed is 
exhausted first, as shown by a rise in conductance until the cation-bed 
effluent passes unchanged through it. The subsequent exhaustion of 
the cation bed is indicated by a drop in conductance to that of the 
influent. 

After various runs, the beds were separated into vertical sections 
and treated with regenerant solutions to study the nature of the proc- 
ess. The Dowex 50 bed was regenerated with acid, and was found 
to be almost entirely in the sodium state, with small additional 
amounts of aluminum and potassium. No silver could be detected. 



( LOG OF SPECIFIC CONDUCTANCE 
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D 2 4 6 8 10 \i 14 16 18 20 2.i 24 26 



ML. OF SYNTHETIC USED FIX 
Fig. 4 

The lonac A 300 bed at the conclusion of a run was coated with a 
black precipitate, probably silver sulfide. When this bed was sec- 
tioned and regenerated, all of the silver added to the system was re- 
covered from the upper third of the bed. However, the black dis- 
coloration did not seem to be affected. Thus, the silver was absorbed 
for the most part as the silver-thiosulfate complex, and is readily 
available for recovery. Most of the added thiosulfate was recovered 
in that form, indicating that it was absorbed before decomposition. 

The demineralization unit is regenerable, and repeated cycles 
showed no significant changes in capacity. 

The amount of fix solution which is imparted to wash water by 
photographic prints was determined by developing and fixing a quan- 
tity of exposed paper, then removing the excess liquid with a roller 



190 GREGOR AND SHERMAN August 

squeegee, followed by washing all the fix out of the paper. It was 
found that to wash one thousand 8- X 10-inch prints, a unit having a 
bed volume of approximately 5 liters would be required. Prints 
washed in this demineralized water were compared with ones washed 
in distilled water; no differences were observed. The stability and 
clarity of the prints were unchanged, as shown by "Fadometer" 
tests. 

Other demineralization processes were also tested. By the use of a 
strong-base anion exchange resin ahead of a cation resin, the normal 
cycle can be reversed. Thus, neutral salts in the influent are con- 
verted to their corresponding hydroxides by the anion bed, followed by 
base absorption in the cation bed. In this experiment the anion ex- 
change resin Amberlite IRA-400,* which has most of its capacity in 
the form of strongly basic groups, was used. This bed was followed by 
one of Dowex 50. While this demineralization system produced a good 
grade of wash water, its capacity was considerably less than that of 
the one adopted. 

The use of a weak-acid cation exchange resin was also investigated. 
When a carboxyl resin is used in conjunction with an anion exchange 
bed, demineralization can occur. The small amount of acid formed 
upon the first pass is absorbed by the anion bed, and the neutral 
effluent upon recycling can have more of its cations converted to acid 
and be absorbed. This system was investigated, using Amberlite 
IRC-50* as the weak-acid cation exchange resin, and lonac A-300 as 
the anion exchange resin. This system was able to demineralize wash 
water. However, the rate of the process was much too slow for print- 
washing. Also, the quality of water produced was poor. 

The applicability of this method for color-process work was demon- 
strated by developing identical batches of Ansco color film simul- 
taneously, one being washed in tap water and the other using the 
demineralization apparatus. The developing outfit was Type 2. No 
detectable difference in the quality of the two prints appeared. It 
has been observed that reticulation of film occurs in some instances 
where wash water of too high purity is used, due to the excessive 
swelling of the emulsion caused by osmotic pressure. This can be 
avoided for the demineralization process by adding a small amount of a 
nonelectrolyte, as urea, to the water, since compounds of this type are 
not affected by ion exchange. 

* Rohm and Haas Co., Philadelphia, Pennsylvania. 



1949 DEMINERALIZATION OF WASH WATER 191 



( 'ori 



ACKNOWLEDGMENT 

'he authors wish to express thanks to the United States Signal 
orps for its support of this investigation, which was carried out under 
Contract No. 36-039 sc-36812 of the Signal Corps Engineering Labora- 
tories, Fort Monmouth, New Jersey. 



REFERENCES 



) H. P. Gregor and J. I. Bregman, "Characterization of ion exchange resins," 

mer. Ghent. Soc., vol. 70, pp. 2370-2373; February, 1948. 

(2) R. B. Atkinson and V. C. Shaner, "Chemical analysis of photographic 
developers and fixing baths," J. Soc. Mot. Pict. Eng., vol. 34, pp. 485-524; May' 
1940. 

DISCUSSION 

MR. JOHN I. CRABTREE: Does it not require a CDiisiderable amount of water 
to wash out the acid and alkali when regenerating the resins? 

DR. HARRY P. GREGOR: It does require considerable amounts of water to rinse 
the beds after regeneration, two or three times the bed volume as a minimum. 
Since one quart of resin bed delivers the equivalent of 200 quarts of wash water, 
this will reduce the conservation factor from 1:200 to 1:66. 

MR. CRABTREE: We have usually found that about six volumes of water are 
about the minimum to wash the bed, carry the regenerant, and accomplish the 
required rinsing of the bed after regeneration. What weight of resin is required 
per liter of fixing bath? 

DR. GREGOR: Our data primarily are based on volume rather than weight. 
One quart of resin in water has a weight of approximately 1.2 kilograms. This 
will absorb about one-half quart of used fix solution. 

MR. CRABTREE: Have you compared the efficiency of this method with the 
cascade system of rinsing in successive tanks, where you replace the first tank 
with the second tank, and so on? 

DR. GREGOR: As I understand it, the United States Signal Corps specification 
of one quart of wash water required for each 8- X 10-inch print is based on the 
countercurrent system you describe. 

MR. CRABTREE: Assuming that the new ion exchange agents described are 
actually as efficient as indicated and can be regenerated with so little water, 
there is still to be considered the weight of the apparatus, the weight of the 
regenerants, and the fact that materials such as hydrochloric acid and caustic 
soda, because of their hazardous nature, require somewhat more substantial con- 
tainers than would the equivalent volume of water. We decided in our work some 
years ago that the matter simmered down to a question of whether the shipping 
space would be more efficiently used to carry extra wash water or the apparatus 
and chemicals required for deionization and decided that there was little if any 
choice between the two. 

In the Army Medical Services they give the film a dip for a second or so in 
water and then squeegee the film between two sheets of transparent sheeting such 
as Kodapak. The film can then be handled like a dry film and can be washed at a 



192 



GREGOR AND SHERMAN 



later date after stripping away the sheeting. I do not see any object in trying to 
get a high-quality film or print right in the field when water is at a premium. 
It is probable also that the concentration of fixing bath in the wash water would 
be greater than 1 per cent. Have tests been made with more concentrated 
solutions? 

DR. GREGOR: The units which we have developed for the Signal Corps are not 
designed to be regenerated under field conditions, but employ replaceable cart- 
ridge units which are used once and then sent back to a base area for regeneration. 
Since one quart of resin must be transported instead of 200 quarts of water, this 
constitutes a satisfactory solution to the logistical problem. We have been able 
to regenerate these units and recover the silver readily. However, this procedure 
applies best to commercial uses and to operations that can be carried out at a base 
area rather than to front-line conditions. 

I do not know why the Signal Corps specifies washing of the prints rather than 
the process you describe. We have carried out our work within the frame of 
reference of the Service specifications. 

In regard to the presence of fixing chemicals in the wash water, this was less 
than 0.001 per cent. The process was efficient to the extent that the purity of the 
wash water was greater than that of distilled water. As a consequence, the prob- 
lem of delineating the upper limit of the amounts of fixing chemicals which can 
remain in the wash water, did not arise. 



Meetings of Other Societies 



August 

Institute of Radio Engineers West 

Coast Convention 
September 

Illuminating Engineering Society 
National Technical Conference 
National Electronics Conference 

October- 
Photographic Society of America 

Convention 
Optical Society of America 

Annual Meeting 
O ctober-November 
Radio Fall Meeting 
Joint IRE-RMA 
March, 1950 
Institute of Radio Engineers 

National Convention 
Optical Society of America 
Winter Meeting 



August 30 through September 2 
San Francisco, California 

September 19 through September 23 
French Lick, Indiana 
September 26 through September 28 
Chicago, Illinois 

October 19 through October 22 
St. Louis, Missouri 
October 27 through October 29 
Buffalo, New York 

October 31 through November 1 
Syracuse, New York 

March 6 through March 9 
New York, New York 
March 9 through March 1 1 
New York, New York 



Film Vaults : Construction and Use* 

BY JOHN G. BRADLEY 

MOTION PICTURE CONSULTANT FOR THE LIBRARY OF CONGRESS, 
WASHINGTON, D. C., ON FURLOUGH STATUS 

Summary The presently accepted type of film-storage vaults and the 
standards governing their use are reviewed. The discussion is made in 
terms of vent area per film load and the resulting pressures; horizontal 
versus vertical arrangement of film cans; open rack, shelf, and cabinet 
storage; units of risk for material of high subject-matter values; air con- 
ditioning; and related problems. Special mention is made of an insulating 
retractor belt for shelf storage. 

INTRODUCTION 

THE RECENT ADVENT of a new safety film base, l intended to replace 
some of the present film bases, merits preliminary comment in 
connection with this discussion. Substantial claims are made for its 
projection life as compared to the acetate safety film, for its safety 
characteristics as compared to the nitrate film, and for its chemical 
stability. It is hoped that before many years its superiority in all 
respects will have been demonstrated and that at least the use of the 
highly inflammable and chemically unstable nitrate film no longer will 
be necessary. 

This long-range solution of the problem does not, however, account 
for the vast accumulations of nitrate film, much of which should be 
copied immediately, or for which added protection should be pro- 
vided. Because a transfer of accumulated nitrate film to a safety base 
is expensive, beyond the current budgets of many film custodians, it 
appears that a nitrate-film-storage problem still exists and will con- 
tinue to exist for many years to come. For the further reason that 
serious losses continue under present standards of vault construction 
and use, a review of the entire problem seems to be in order at this 
time. While this discussion emphasizes the hazards of nitrate film, it 
does not ignore the need for adequate protection of other types of 
record material of high value. 

THE GENERAL PROBLEM STATED 
Proper film storage (aside from the protection it should give the 

* Presented October 25, 1948, at the SMPE Convention in Washington. 

AUGUST, 1949 JOURNAL OF THE SMPE VOLUME 53 193 



194 BRADLEY August 

working staff) should reduce to a minimum the risk of loss from fire, 
water, and chemical deterioration. The average vault in current use 
does not meet these requirements. Fires continue at an uncomfort- 
able rate, damage from water in an attempt to control such fires re- 
mains serious, and the application of known chemical preservation 
techniques is frequently difficult if not impossible. In this latter re- 
spect, the chemist and the custodian have gone ahead of both the 
underwriter and the architect. In fact, our national thinking in 
terms of vault construction and storage practices seems to have come 
to a halt many years ago. 

For example, the Underwriters' Laboratories, the National Board of 
Fire Underwriters, municipalities, and others in a position to speak 
with authority on the subject, still approve the storing of 7 pounds of 
nitrate film for each square inch of vent area, still require heavy and 
expensive construction to prevent a rupture of the vault by reason of 
fire and internal pressure, still approve up to 10,000 pounds of film 
per vault unit regardless of the subject-matter value of such film, and 
still recommend the storing of cans on edges in both vaults and 
cabinets, which exposes the film to damage by water. On the subject 
of temperature and humidity control these same authorities are almost 
completely silent. These are the facts; what are the implications? 

Neither experience nor experiment supports such practices, par- 
ticularly when the protection of archival or other material of high 
value is involved. Certainly a cabinet in which each can of film is 
stored horizontally in a separate compartment that is vented to the 
exterior, as advocated by Crabtree and Ives 2 19 years ago offers 
greater protection against both fire and water than a vault where the 
cans are stored on edge in open racks. Certainly the need for protec- 
tion against high pressures and chemical deterioration has been amply 
demonstrated in recent years. Perhaps the apparent discrepancy 
between existing regulations and recently developed information is the 
fact that such regulations have not been thoroughly revised in several 
years, a discrepancy we hope will be corrected shortly. 

Perhaps a better explanation is a matter of misplaced responsi- 
bility. For example, the architect is not supposed to be a chemist or a 
custodian. He builds for others and in the terms that others dictate. 
The underwriter's interest in fire control is based chiefly on a possible 
loss of property. He is a sort of scientific gambler; he takes a cal- 
culated risk and if he loses he pays the debt, but not by replacing a 
priceless record. He bets against lightning striking the storage building. 



1949 FILM VAULTS 195 

someone winding a film too fast or dropping it, on a concrete floor, 
excess humidity and overheating, short circuits, and other causes of 
61m fires. He bets on the average and pays off on the exception. It is 
lot his responsibility to worry about the exception even though it 
ivolves an irreplaceable item. Theoretically it is no concern of 
ither the architect or the underwriter if the custodian wants to store 
is of both primary and secondary value in one vault as the unit 

risk. But it is the custodian's fault if he fails to distinguish between 

ich values and demand protection accordingly. 

Fortunately such a distinction is being made now as never before 
and the need for greater protection appears more important by con- 
trast. People are becoming more preservation-conscious. Sharper 
separations are being made among record materials of different values. 
The reissue value of some of the old classics is becoming increasingly 
obvious. Producers realize that the genius portrayed in a particular 
production may be impossible to recapture; while many of the 
factual pictures that record situations in time and place that cannot 
be reassembled, or that depict persons no longer living, have become 
priceless. The custodian is becoming an archivist. 

It appears, therefore, that one of the basic prerequisites of appro- 
priate vault construction and use is an appraisal of the material to be 
stored in terms of the protection required. 

OPEN-RACK STORAGE TERTIARY PROTECTION 

In these terms, let us examine a typical film vault currently in use. 

contains 750 cubic feet and has an authorized storage capacity of 

),000 pounds of nitrate film. In the 35-mm size, this amounts to 
>me 2,000,000 feet, 2000 reels, or 200 ten-reel subjects. If all the 
material so stored represented camera negatives or archival items in 
any form, it is conceivable that one vault might house irreplaceable 
property costing 20 or 30 million dollars (or more) to produce, to say 
nothing of other costs such as human life, in the case of war pictures. 
This is a dangerous procedure, particularly when it is now a well- 
' known fact that all the film so stored may be lost or seriously damaged 
.in case of fire. It is obvious that in such a case such a risk is too great. 
Only when the film stored represents material of tertiary value such 
as worn and duplicate prints, could such a unit risk be justified. 

Let us examine this vault further. It has a vent of one square inch 
for each 7 pounds of nitrate film or a total of 1400 square inches for the 
vault. Experiments conducted under high governmental and 



196 BRADLEY August 

scientific auspices over the last few years have proved conclusively that 
such a limitation of vent to film load is dangerous, that it will produce 
pressures on the borderline of explosions, and that a rupture of the 
vault may and frequently does result. In case of such a rupture, 
neighboring vaults are involved in the losses, as actual incidents on 
record indicate. 

A vent of 1 square inch for not more than 5 pounds of film is recom- 
mended ; or to state the matter another way where vaults are already 
constructed, not more than 5 pounds of film for each square inch of 
vent should be allowed. With such a ratio, no serious pressure is 
likely. 

Let us examine this typical vault still further but this time in terms 
of the arrangements of film cans, and the habits of (nitrate) film fires 
on which recent experiments have thrown much light. For example, 
the typical vault is designed for open-rack storage with the cans 
placed on edge. Upright partitions extending from floor to ceiling 
divide these racks into sections 36 inches wide each. This arrange- 
ment provides for the storing of some 20 or 25 cans (depending on 
their thickness) side by side on each rack in each section. There are 
no horizontal separations between racks so that an open space exists 
from the floor to the ceiling. Experiments have shown that if the 
film in one can ignites, the fire will spread sideways to the adjacent 
cans at intervals of less than five seconds. The fire will also spread 
vertically to floor and ceiling. In this case, the section is the unit of 
risk. But that is not all; the fire may jump across the aisle and in- 
volve the film on the other side of the vault and cross-fire back and 
forth until the entire contents of the vault are involved. If the water 
system should fail, the duration of the fire is generally less than three 
minutes. If the water system does not fail and the sprinkler heads 
operate properly, the spread of fire will be slower but may, and fre- 
quently does, involve the entire vault. If, by chance, some of the 
film escapes the fire, it is likely to be damaged by water. 

In such a circumstance, the gamble is that there will be no fire; 
for it can be seen that if a fire occurs, the protection is negligible. 
Or, granting the possibility of a fire, the gamble is that the water 
sprinklers will operate, that the progress of the fire will be retarded, 
that the pressure will not rupture the vault, and that the loss will be 
limited to the original vault involved. Let it be repeated that only 
when the material stored represents tertiary values or items that can 
be easily and cheaply replaced, could such a risk be justified. 



1949 



FILM VAULTS 



197 



SHELF STORAGE SECONDARY PROTECTION 

If the custodian does not want to take the risks inherent in open- 
rack storage (just described), two solutions to his problem are sug- 
gested: (1) shelf storage for films of secondary values and (2) cabinet 
storage for films of primary values. Both shelf and cabinet storage, 
designed by the author several years ago, may be found in the Na- 
tional Archives Building, Washington, D. C., but are discussed here 
with certain improvements suggested. 

In the case of shelf storage, the cans are stored flat to prevent 
damage from water. The upright partitions are increased in number 

I Aj 



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^ SCUPPER. 

Fig. 1 Side-view elevation. A, flue to exterior; B, ceiling or roof line; 
C, sprinkler heads; D, floor. 

from one every 36 inches (open-rack storage) to one approximately 
every 12 inches; that is, one for each tier of film cans. Such prox- 
imity of partitions limits the unit load involved in the horizontal 
spread of fire. (See Fig. 1.) The shelves are solid with a maximum of 
heat resistance and a minimum of heat conductivity and serve as 
insulators against a vertical spread of fire. (See Fig. 2.) 

NOTE : In some instances where horizontal storage has been adopted, 
the cans rest on short flanges that are anchored to the sides of the 
upright partitions. In such a case it is argued that the use of such 
flanges, instead of solid shelves, allows the water from the sprinkler 
heads to reach each can in full volume. It should be pointed out, 
however, that water by itself may not prevent a spread of a nitrate- 



198 



BRADLEY 



August 



film fire; a vertical spread in this case. With such an arrangement 
the unit risk would be the entire tier of films. 

To compensate for this loss in volume of water when insulating 
shelves are used, directional spray-type sprinkler heads are recom- 
mended. It is also recommended that these heads be so positioned 

I I 

SHEATWEO I* ^ 




Fig. 2 Front-view elevation. A, "blisters" to support cans 
and create air and water space. 



TIERS 



!& 



SUPPUV DOC' 



DOTS.. 

r ~^\~ 



'!!( 



\\i 
\\\ 



\\l 



D 

Fig. 3 End-view elevation. A, roof line; B, water 
sprinklers; C, vault aisle; D, floor line. 

that the spray is thrown at an angle against the outer or exposed 
edges of the cans into the compartments. This is illustrated in 
Fig. 3. 

Insulating Retractor Belt:* Two additional dangers exist with 
respect to shelf storage that merit comment; heat conduction and 
cross fire. NOTE : The directional spray, mentioned above, will reduce 
the danger of cross fire but it may not eliminate it. In connection 
* Patent pending. 



1949 



FILM VAULTS 



199 



IN SU LATINO 
RETRACTOR. EUT 
PARTIALLY 




Fig. 4 Side-view elevation. A, "blisters" to support cans; B, can in place; 
B r , can partially withdrawn. 




CROSS SECTION OF PARTITION 



RING (.SEE 

5ITIONINO SLOT 
RETRACTOR BEUT H PL^CE 



AMCUOft R.1VETS 



Unto 

RtTRACTO- 
TfMj-V PRAWH GOT 
- CAM PlkRTllkLLY OUT 



ANCHOR. 



Fig, 5 Plan showing operation of retractor belt. 



200 



BRADLEY 



August 



with both these dangers, attention is called to the above-mentioned 
belt, the principal functions of which are listed below. 

(1) As a retractor device to pull the can from the compartment un- 
til it can be gripped by the fingers as illustrated in Figs. 4 and 5. 
With this device the compartment can be made smaller so that the 
total space saved in the vault is considerable. As a retractor device, 
the belt is applicable to both nitrate and safety film. 

(2) As an insulating device to separate the metal partitions from 
the metal cans and thus minimize the danger of heat conduction from 
the one to the other as illustrated in Fig. 5. 

(3) Again, as an insulating device to protect the front edges of the 



KOTE-. 

FIGURE. G 15 T14E SAME 
A* FI&URE 5 EXCEPT THAT 

THE CTR*CTO. 
)* LONGER. AND 
ACROSS THE FRONT OP TWE C*N 
TO PROTECT FILM AGAINST 
DA NOte OF CROSS-FIRE 




RM4G 



&>< MOCK 



Fig. 6 Plan. A, positioning slot; B, anchor rivets; C, cross section of par- 
tition. 

cans from the heat on the opposite side of the vault and thus lessen 
the danger of cross fire. (See Fig. 6.) 

The insulating retractor belt can be made of any fire-resistant 
material such as asbestos or spun glass, woven to give it tensile 
strength. Its width should be approximately the same as the height 
of the can. It is anchored to one of the upright partitions, encircles 
the sides and back of the can, and runs through a positioning slot or 
guide on the opposite upright partition. If other means have been 
provided for protecting the front edges of the can (as will be sug- 
gested later in this discussion) or if safety film only is involved, the 
belt terminates just in front of the positioning slot with a hinged ring 
in its tapered end for easy handling. If, however, it is to be used as a 
protection against cross fire, it is extended across the face of the can 
to the original anchor point where its end ring is secured by a hook as 
illustrated in Fig. 6. When so used, the belt does not prevent water 



1949 



FILM VAULTS 



201 



from entering the compartment in sufficient quantity for cooling pur- 
poses nor will it cause flooding of the film; there is ample space under 
its front part for drainage. 

Fire and Water Baffles: Another means of protecting the front 
edges of the cans from cross fire consists of two hinged baffles, an- 
chored at the front of the compartment as illustrated in Fig. 7. The 
lower baffle extends upward to a vertical height of approximately 
*/4 inch and outward (into the vault aisle) at an angle of about 40 
degrees. The two triangular spaces at the ends of this baffle are en- 
closed and the baffle is held in place by a spring. This spring permits 
it to swing downward when the can is being removed from or inserted 
into the compartment. The upper baffle hangs in a vertical position 
of its own weight. The two baffles, when in normal position, slightly 

x-FIRfe RfcSlSTAWT SWfcLF-y 



/ 

/I 



E 



FILM CAN 





A 

Fig. 7 Side-view elevation. A, hinges; B and C, baffles 
in place; B' and ' baffles open. 

overlap, and thus protect the can from cross fire. The lower baffle 
serves the additional purpose of diverting water from the sprinkler 
heads into the compartment for cooling purposes; its limited height 
prevents flooding of the film. 

The baffles may be opened, for inserting or removing the can, 
either by a simple bell-crank mechanism or by the use of the retractor 
belt. In the latter case, the shorter version of the belt is used as 
shown in Figs. 4 and 5. Its ring and about l / inch of its tapered end 
are drawn through a slot in the lower part and one end of the upper 
baffle. About 6 inches of the front end of the belt is stiffened so that 
when it is pulled outward, it lifts the upper baffle and forces the lower 
baffle down. (See Fig. 8.) Both baffles remain open until the can is 
replaced and the belt pushed back into position. 

Still another protection against the danger of cross fire is the use of 
half vaults; that is, films stored only on one side of the vault. In 
such a case, the cross fire from an affected compartment would strike 






202 BRADLEY August 

the opposite wall where its force and heat would be reduced. This 
would be particularly true after the water sprinklers operated and the 
wall was kept wet with a sheet of flowing water. 

NOTE: The suggestions covering the use of the insulating retractor 
belt, fire and water baffles, and half-vault storage are offered largely 
on the basis of theory, without the benefit of extended experiment. 
The theory is derived, however, from experiments with comparable 
situations and is believed to be sound. 

As a further precaution against heat conduction, particularly in a 
vertical direction, it is recommended that air space be provided be- 
tween the can and the shelf on which it rests. This can be done easily 
by ridges or "blisters" about 1 / 8 inch in height either on the upper 
surface of the shelf or on the bottom of the can. (See Figs. 2 and 4.) 




Fig. 8 Side-view elevation. A, upper baffle in open position; B, lower 
baffle open; C, ring and retractor belt partially withdrawn. 

The cost of shelf storage herein described is not excessive in terms 
of the protection it provides. Perhaps the greatest objection is the 
loss in storage load per vault. This is not serious, however, because a 
vault of normal size will house nearly 1000 reels of 35-mm film with 
the tiers extending only 6 feet high. Such a load is not too far below 
that actually carried in general practice. 

While there may be some risk of initial loss in shelf storage, before 
the sprinkler heads operate, such a risk is negligible when compared to 
the risk in open-rack storage. 

CABINET STORAGE PRIMARY PROTECTION 

If the custodian wants maximum protection for material of maxi- 
mum value as well as maximum safety for personnel, cabinet storage 
is recommended. 

Both insulated and uninsulated cabinets have been described pre- 
viously 3 " 6 and will not be discussed here except briefly, and in terms of 






FILM VAULTS 



203 



itruction and installation problems. The uninsulated or waler- 
cascade cabinet, which is the more economical to install, will be 
as a typical solution to the problem posed. 

The basic principle of the water-seal cabinet, stated briefly for the 
convenience of the reader, is a diversion of heat from the storage area 
of the cabinet into a common flue, and the introduction of water into 
the cabinet where it flows over, under, and around each film can. 
The source of the water is an automatic directional spray-type sprin- 
kler head. Each film is stored horizontally in a metal can, and in a 
separate compartment that is vented to the common flue. The 
cabinet can be designed for either 1000- or 2000-foot reels of film and 
for as many of each as needed in either the 35-mm or 16-mm size. 




VEP-TICAX- FLUt 



SWATTER OLA.SS 

OR. FLUTTER. MEMBRANE. 
ROOF LEVEL 



OR. CONDUIT 



SIDE WALL VlfeW OP VA.UL.T 



- y-r " " 

V SCUFPER, 

Fig. 9 Side-view elevation. A, cabinet flues; B, water-supply line. 
For the sake of illustrating the construction problem under con- 
leration, however, a cabinet that will hold 24 1000-foot, 35-mm 
jls is cited. It consists of a 4-inch drain base, a 72-inch storage 
;tion, and an 8-inch hood containing the water sprinkler. The over- 
height is, therefore, 84 inches. The topmost can is 76 inches from 
3 floor, or within easy reaching distance without the use of a foot- 
)1 or ladder. The installation of this cabinet requires either a hung 
tiling, or a conduit over each row of cabinets, into which the upper 
part of the flue is inserted. Fig. 9 shows a side view and Fig. 10 
shows an end view of such an installation. Fig. 11 shows a ceiling 
plan with the use of conduits. Fig. 12 shows an enlargement of a 
hood near the juncture of the ceiling or conduit. 



204 



BRADLEY 



August 



The unit of risk is one reel or 5 pounds of film. Extended experi- 
ments indicate that an incipient fire inside the cabinet will not spread, 
nor will an external fire penetrate the cabinet. All fumes are filtered 
and siphoned off to the outer air. By reason of its airtight constn c- 
tion and the water-seal drain base, combustion seldom takes the form 
of a flame; hence the total heat is kept to a minimum for this type of 
fire. In the remote event that the water supply failed, the spread of 
fire (if any) would be very slow, and fire fighters could enter the vault 
and manually put the fire under control; that is, stop its spread by 
cooling the unaffected cabinets until the original or incipient fire 
burned out. This would not be practicable or advisable in the case of 
open-rack or shelf storage. 

^F. A. SUPPLY \ 





M.P. 


NM 


U.P. 


W.P. 


NV; 


U.P. 






i X 














s \ ' 






/ X 1 








i^ ii) 






I/ \l 






W ATfcR. "SUPPLY 3 


^ 




r 






/ 
* 


^ 


V 








ul 






E 
















2 










1L 






i 










\ VAULT 


*L. 


J 









C 

Fig. 10 End-view elevation. A, roof line; B, con- 
duit or hung ceiling line; C, floor; HF, horizontal 
flues or conduits. 

The custodian may, if he wishes, provide a reserve water-storage 
tank as insurance against a possible failure of the municipal water 
supply. It should be noted that the aperture of the sprinkler head 
recommended is only 3 / 8 inch and delivers approximately 15 gallons 
of water a minute. It should also be noted that seldom will more than 
one sprinkler head be involved at any one time. In these terms, it 
can be seen that a reserve tank holding only 500 gallons would last 
some 25 minutes, or long enough for the incipient fire to burn out. 

Another feature of the water-seal cabinet, recently developed and 
not previously reported in the JOURNAL, is a heat-conducting element. 
(See Fig. 12.) The purpose of this element is to accelerate the opera- 
tion of the sprinkler head in case of an external fire; that is, a fire 
simulating a burning-building condition. NOTE: The average time 
required for the sprinkler head to operate during an internal fire is 



1949 



FILM VAULTS 



205 



about 20 seconds after ignition. Preliminary tests with external fires 
indicate that the sprinkler head will operate within about the same 
time after the fire has contacted the heat-conducting element. 



HOfUZONTAX. FUUE4 Oft CONDUITS 




Fig. 11 Ceiling or conduit plan. 




Fig. 12 Side-view elevation. A, ceiling or conduit line; B, fire 
trap open; B', fire trap closed; C, spray-type water sprinkler. 

MISCELLANEOUS CONSIDERATIONS 

A suitable air-conditioning system, properly trapped against back- 
, is recommended for all storage where material of high value is 
involved and where long-range preservation is a part of the problem. 
Figs. 1 and 3 show such an installation. If no air-conditioning system 
has been provided for existing vaults, dehumidifying units are recom- 
mended; these represent no serious installation problem. 

Not only should drains of ample capacity be included in all sprin- 
klered vaults, but means should be provided for keeping such drains 
open to full capacity; otherwise, a collapse of the floor from the 






206 BRADLEY 

weight of the water may result. For wall scuppers, a picket guard is 
suggested to prevent coarse material from entering and clogging the 
openings. 

Prevailing regulations stipulate a limit for both the load of nitrate 
film stored (10,000 pounds) and the size of the vault (750 cubic feet). 
In terms of cubic footage, this means (among other possible dimen- 
sions) a vault 16 feet long, 5 J /2 feet wide, and S 1 /^ feet high. For 
cabinet storage of the type described, the load limit within these 
dimensions is about 700 reels of 35-mm film. A vault 16 feet long 
also represents a convenient limit in terms of water-supply lines and 
sprinkler heads if bulkiness in the supply lines is to be avoided. 

In many instances, however, smaller vaults will be an advantage 
for the reason (among others) that cheaper construction may be em- 
ployed. For example, the National Board of Fire Underwriters 7 
approves vaults or work-storage rooms with metal-lath and plaster 
walls only 2y 2 inches thick (among other thicknesses prescribed), 
providing cabinets are used. Up to 200 standard rolls may be so 
stored. See subsection 112 (a) of the NBFU Regulations. Among 
the places where such construction and cabinet storage is presently 
approved are work rooms, projection booths, rewinding rooms, ship- 
ping rooms, and studios. 

In the design of new vault buildings where a row of vaults for each 
side of a common corridor is planned, it is recommended that the 
vault doors be staggered so that they do not face each other. It is 
also recommended that long narrow vaults be avoided; ample aisle 
space is not an extravagance. 

REFERENCES 

(1) Charles R. Fordyce, "Improved safety motion picture film support," /. 
Soc. Mot. Pid. Eng., vol. 51, pp. 331-351; October, 1948. 

(2) J. I. Crabtree and C. E. Ives, "The storage of valuable motion picture film," 
/. Soc. Mot. Pid. Eng., vol. 15, pp. 289-306; September, 1930. 

(3) John G. Bradley, "Motion pictures as government archives," /. Soc. Mot. 
Pid. Eng., vol. 26, pp. 653-661; June, 1936. 

(4) Report of the Committee on Film Preservation, /. Soc. Mot. Pid. Eng., 
vol. 27, pp. 147-155; August, 1936. 

(5) John G. Bradley, "Changing aspects of the film-storage problem," J. Soc. 
Mot. Pid. Eng., vol. 30, pp. 303-318; March, 1938. 

(6) Report of the Committee on Preservation of Film, /. Soc. Mot. Pid. Eng., 
vol. 35, pp. 584-607; December, 1940. 

(7) Regulations of the National Board of Fire Underwriters for Nitrocellulose 
Motion Picture Film, New York, N. Y., 1939. Pamphlet No. 40. 



66th Semiannual Convention 
SOCIETY OF MOTION PICTURE ENGINEERS 

Hollywood-Roosevelt Hotel October 10-14, 1949 
Hollywood, California 


OFFICERS IN CHARGE 

EARL I. SPONABLE President 

LOREN L. RYDER Past-President 

PETER MOLE Executive Vice-President 

JOHN A. MAURER Engineering V ice-President 

CLYDE R. KEITH Editorial Vice-President 

DAVID B. JOY Financial V ice-President 

WILLIAM C. KUNZMANN Convention V ice-President 

ROBERT M. CORBIN Secretary 

RALPH B. AUSTRIAN Treasurer 

General Office, New York 

BOYCE NEMEC Executive Secretary 

HELEN M. STOTE Journal Editor 

WILLIAM H. DEACY, JR Staff Engineer 

SIGMUND M. MUSKAT Office Manager 

Chairmen of Committees for the Convention Program 

Convention Vice-President W. C. KUNZMANN 

Pacific Coast Section and Local Arrangements S. P. SOLOW 

Papers Committee Chairman N. L. SIMMONS 

Vice-Chairman, Hollywood L. D. GRIGNON 

Vice-Chairman, New York E. S. SEELEY 

Vice-Chairman, Chicago R. T. VAN NIMAN 

Vice-Chairman, Washington J. E. AIKEN 

Vice-Chairman, Montreal H. S. WALKER 

Publicity Committee Chairman HAROLD DESFOR 

Vice-Chairman, West Coast Announced Later 

Registration and Information C. W. HANDLEY 

Assisted by W. L. FARLEY and R. H. DUVAL 

Luncheon and Banquet J. P. LIVADARY 

Hotel Housing and Reservations WATSON JONES 

Membership and Subscriptions LEE JONES 

West Coast Vice-Chairman G. C. MISENER 

Ladies' Reception Committee Hostess MRS. PETER MOLE 

Transportation Rail, Plane, Local HERBERT GRIFFIN 

Public-Address Equipment LLOYD T. GOLDSMITH 

Projection Program Committee 35-Mm R. H. McCuLLOUGH 

Assisted by Members of Los Angeles Projectionists Local 150 

Projection Program Committee 16-Mm H. W. REMERSCHEID, 

E. C. FRITTS 

207 



208 66TH SEMIANNUAL CONVENTION August 

GENERAL INFORMATION 

HOTEL RESERVATIONS AND RATES The Housing Committee, under 

Watson Jones, chairman, will make 

reservations for members and guests. Inform him at 1560 North Vine Street, 
Hollywood 28, California, of the accommodations you desire. He will book your 
reservations and confirm them. 

TRAVEL Make your train or plane reservations early because West Coast 
travel in October normally is quite heavy. 

PAPERS PROGRAM Authors who plan to prepare papers for presentation at 
the 66th Convention should write at once for Authors' 

Forms and important instructions to the Papers Committee member listed below 
who is nearest. Authors' Forms, titles, and abstracts must be in the hands of 
Mr. Grignon by August 15 to be included in the Tentative Program, which will 
be mailed to members thirty days before the Convention. 
N. L. SIMMONS, Chairman E. S. SEELEY, Vice-Chairman 

6706 Santa Monica Blvd. Altec Service Corp. 

Hollywood 38, California 161 Sixth Ave. 

J. E. AIKEN, Vice-Chairman New York 13 New York 

116 N. Galveston St. R " T " VAN NlMAN > Vice-Chairman 
Arlington, Virginia 4501 Washington Blvd. 

Chicago 24, Illinois 

LORIN GRIGNON, Vice-Chairman H. S. WALKER, Vice-Chairman 
20th Century-Fox Films Corp. 1620 Notre Dame St., W. 

Beverly Hills, California Montreal, Que., Canada 

CONVENTION GET-TOGETHER LUNCHEON The 66th Semiannual Con- 
vention Get - Together 

Luncheon for members, guests, and ladies attending the Convention will be held 
in the Blossom Room on Monday, October 10, at 12:30 P.M. There will be emi- 
nent speakers and entertainment. 

Most important Luncheon seating will only be guaranteed and assured if 
tickets have been procured prior to the Convention from W. C. Kunzmann, 
Convention Vice-President, or before 11:00 A.M. on October 10 at Registration 
Headquarters. 

Checks or money orders issued for Registration fees, Luncheon, or Banquet 
tickets should be made payable to W. C. Kunzmann, Convention Vice-President, 
and not to the Society. 

BANQUET AND COCKTAIL The Convention Cocktail Hour for holders 
HOUR of Banquet tickets will be held in the Redwood 

Room on the mezzanine floor, on Wednesday evening, October 12, between 7: 15 
P.M. and 8:15 P.M. 

The Banquet (dress optional) will be held in the Blossom Room on Wednesday 
evening, October 12, promptly at 8:30 P.M. 

There will be entertainment and dancing, and at this time the Annual Awards 
will be made. 

NOTE: Tables for the Banquet can be reserved at registration headquarters 
prior to noon on October 12. 



1949 



66TH SEMIANNUAL CONVENTION 



209 



LADIES AND GUESTS Members are encouraged to invite their friends to 
attend the Convention. There will be eleven Tech- 
nical Sessions open to all who wish to be on hand, and for the ladies who accom- 
pany their husbands, the Ladies' Committee is arranging a week of sight-seeing 
and special events. The Ladies 7 Registration Headquarters will be located in 
parlor suite 420-421 in the Hollywood-Roosevelt Hotel. The ladies attending 
the Convention should register and receive their badges, identification cards, 
and programs. Mrs. Peter Mole will serve as Hostess. 

RECREATION The identification cards issued to members and guests who 
register for the Convention will permit them to attend Grau- 
man's Chinese and Egyptian Theaters of the Fox West Coast Circuit, the Holly- 
wood Paramount, the Pantages, and Warner Theaters, all of which are located 
on Hollywood Boulevard and near the hotel. Convention Headquarters will 
have a wealth of information on places to visit in or near the Los Angeles area. 



TENTATIVE 
Monday, October 10, 1949 

9 : 30 A.M. REGISTRATION 

Mezzanine Floor 

ADVANCE SALE OF 
LUNCHEON AND BAN- 
QUET TICKETS 

12: 30 P.M. GET-TOGETHER LUNCH- 
EON 
Blossom Room 

3: 00 P.M. CONVENING SESSION 
Blossom Room 

8:00 P.M. TECHNICAL SESSION 
Blossom Room 

Tuesday, October 11, 1949 

10 : 00 A.M. TECHNICAL SESSION 
Blossom Room 

2: 00 P.M. TECHNICAL SESSION 
Blossom Room 

8:00 P.M. TECHNICAL SESSION 
Blossom Room 



PROGRAM 

Wednesday, October 12, 1949 

10 : 00 A.M. HIGH-SPEED PHOTOG- 
RAPHY SESSION 
Aviation Room 

2: 00 P.M. HIGH-SPEED PHOTOG- 
RAPHY SESSION 
Aviation Room 

7 : 15-8 : 15 P.M. COCKTAIL HOUR 
Redwood Room 

8:30 P.M. BANQUET AND DANCE 
Blossom Room 

Thursday, October 13, 1949 

OPEN MORNING 
2:00 P.M. TECHNICAL SESSION 

To be announced 
8:00 P.M. TECHNICAL SESSION 

To be announced 

Friday, October 14, 1949 

OPEN MORNING 
2 : 00 P.M. TECHNICAL SESSION 

Blossom Room 
8:00 P.M. TECHNICAL SESSION 

Blossom Room 
ADJOURNMENT 




JOHN H. KURLANDER 

JOHN H. KURLANDER, head of the projection, photographic, and 
miniature-lamp section in the Westinghouse Lamp Division's 
Commercial engineering department, died June 24, 1949, in Nutley, 
New Jersey. 

During World War II he developed a gunsight lamp which erased 
the blind spots American airmen encountered in firing at enemy 
planes diving out of the sun to attack. 

His peacetime developments included the device that produces 
either a spot of light or flood of light from an ordinary hand flash- 
light; a blue-bulb photoflash lamp emitting invisible, unobtrusive 
light; "black-light" illumination for airplane instrument dials, and 
colored filter glass for automotive turn signals preventing "ghost" 
signals caused by the reflections of sunlight. 

Mr. Kurlander' s early work with photoflash lamps also resulted 
in the design of such a lamp to function dependably with mechanical 
camera-shutter synchronizers. 

From 1930 to 1937, Mr. Kurlander was Secretary of the Society 
of Motion Picture Engineers. He joined the Society as an Active 
member in 1926, and later was elevated to the Fellow grade. He 
also was a member of the Illuminating Engineering Society, the 
American Optical Society, and the Society of Automotive Engineers. 

Mr. Kurlander was graduated from Drexel Institute, Philadel- 
phia, with a Bachelor of Science degree in Electrical Engineering. 

In 1920 he joined the Edison Lamp Works in Harrison as lighting 
engineer. Six years later he became chief engineer of the Brenkert 
Light Projection Company, Detroit, and in 1929 joined the West- 
inghouse Lamp Division in nearby Bloomfield. 



210 



Standards Recommendation 



Proposed Standard for 35-Mm Sprocket Holes 

The April, 1948, JOURNAL published a proposed American Standard for Cutting 
and Perforating Dimensions of 35-Mm Motion Picture Combination Negative and 
Positive Raw Stock for a 90-day period of trial and criticism. A complete history 
of the development of this Standard over the past thirty years was also published. 
At the June 21, 1949, meeting of the Standards Committee the comments which 
had been received were reviewed. 

The principal objections to the adoption of the Standard at this time came from 
representatives of Ansco. They wished additional time before recommending 
adoption of this Standard for the following reasons: 

1. Ansco has a counterproposal which they believe will give better results in so 
far as steadiness in cameras is concerned and from the standpoint of wear during 
projection. Their proposal is a modification of the present Bell and Howell nega- 
tive perforation except that the sharp corners have been rounded with a radius of 
approximately 0.01 inch. 

2. It is their belief that if any combined positive-negative perforation is 
adopted as an American Standard now, existing perforating Standards for negative 
and positive stock should be withdrawn. 

Therefore, because of the objections the Standards Committee decided again to 
return this proposed Standard to the Film Dimensions Committee under the 
chairmanship of Dr. E. K. Carver. It was recommended that additional tests be 
conducted to determine whether or not the Ansco proposal is superior to the 
presently proposed Standard. 



Section Meeting 



Central 

The first paper presented at the May 12, 1949, meeting of the Central Section, 
was delivered by Samuel R. Todd, acting chairman, Chicago Board of Examiners 
of Motion Picture Machine Operators, Chicago Bureau of Electrical Inspection. 
His subject was "Potential Trends for Projection-Room Specifications Due to 
Advent of Acetate Film." The result of his investigation only pointed to the 
fact that no present safety rules could be relaxed. The booth which usually 
houses generator equipment and wiring carrying heavy loads will still have to be 
separated from the audience. Rewind machines still will have to be built of metal 
and enclose the film. Metal storage cabinets must house the film and keep it in 
order for the projectionist to show properly. 

The next paper was entitled, "Adjustment, Care, and Repair of Soundhead 
Optical Systems," by P. V. Smith, of the RCA Service Company. This paper 
outlined the three different types of sound optical systems in present use. The 
breathing action of the lens system or air-pressure changes draws in oil which not 
only destroys the image obtainable, but also attacks the cement between elements. 
The need for laboratory services in restoring these lens systems to usefulness is 
stressed. A laboratory test table with optical bench was described. A test film 
with a tone on either side of the track for centering the image is used in the field. 

211 



New Products 



T^urther information concerning the material described below can 
JL be obtained by writing direct to the manufacturers. As in the case 
of technical papers, publication of these news items does not consti- 
tute endorsement of the manufacturer's statements nor of his products. 



New Westrex Equipment 

Automatic Rewind 

Westrex Corporation, 111 Eighth 
Avenue, New York 11, N. Y., recently 
has made available its automatic re- 
wind for the Westrex RR3S and RR3SP 
re-recorders. 

The AR3 automatic rewind is an op- 
tional accessory for the Westrex RR3S 
and RR3SP re-recorders, providing 




Automatic Rewind 

facilities for rewinding a full reel in less 
than one minute. The automatic re- 
wind includes a 110- volt, Ve-horse- 
power series-wound motor, a motor 
speed control which may be preset to 
the desired rewind speed, and a film- 
roller-operated microswitch which auto- 
matically disconnects the motor when 
the film end passes under the roller. 
212 



The same microswitch is used to turn 
the device on and off, and no other 
operational controls or adjustments are 
required. For rewinding, the rewind 
motor drives the feed reel of the re- 
recorder through a pulley. During the 
running of film through the reproducer, 
the rewind motor idles, being driven 
from the feed spindle. Thus, no clutch 
change-over device is required. The 
automatic rewind has been designed to 
include standard parts which are simple 
and sturdy so that maintenance re- 
quirements may be kept at a minimum. 
The equipment may be easily installed, 
as existing holes are used for mounting 
the motor bracket. 

Double- Film Attachment and Loop 
Adapter 

The Westrex R2-3 double-film at- 
tachment was designed for use with 
Century projectors and Westrex R2, 
R3, or R4 reproducers, and may be 
adapted for installation on certain 
other types of projectors. A projector 
equipped with this attachment may be 
used for reviewing separate picture and 
sound print "rushes," or for re-record- 
ing from a separate sound print. In 
addition, the normal operation of the 
projector is retained. 

The R2-3 double-film attachment 
consists of a large lower magazine, in- 
stalled in place of the Century take-up 
magazine, and two film chutes which 
provide a path for guiding the film 
around the projector. The sound feed 
and take-up reels are located at the left 



New Products 



Further information concerning the material described below can 
be obtained by writing direct to the manufacturers. As in the case 
of technical papers, publication of these news items does not consti- 
tute endorsement of the manufacturer's statements nor of his products. 




Double Film Attachment and Loop Adapter 



in the lower magazine, and the picture 
take-up reel is at the right as viewed 
from the operator's side of the projec- 
tor. The reels are arranged to simplify 
all threading operations. 

The RL2.-3 loop adapter consists of 
a large aluminum film container which 
fits into the lower magazine of the 
R2-3 double-film attachment. This 
optional equipment provides for the 
running of picture and, or, sound loops 
for scoring, dubbing, or re-recording 
purposes. Film loops of between 9 and 
150 feet are accommodated. 

The loop adapter may be rapidly in- 



stalled or removed, being held in posi- 
tion with three knurled screws . Thread- 
ing operations for either reels or loops 
have been greatly simplified as no ex- 
ternal film-guide rollers are required. 

Push- Pull Conversion Parts 

The Westrex Series of P-200 push- 
pull conversion parts for Westrex re- 
recorders consists of a complete optical 
system and a phototube coupler which 
provide for the selective reproduction 
of 100-mil standard, 100-mil push-pull, 
or 200-mil, push-pull 35-mm area or 
density film in the Westrex RR3S re- 

213 



New Products 



Further information concerning the material described below can 
be obtained by writing direct to the manufacturers. As in the case 
of technical papers, publication of these news items does not consti- 
tute endorsement of the manufacturer's statements nor of his products. 



recorder or the Westrex R2, R3, or R4 
reproducers. The push-pull conversion 
parts for the re-recorder and all of the 
reproducers are essentially the same, 
differing only in the mounting brackets 
for some optical parts and the physical 
arrangement of the phototube coupler. 
The basic optical parts include a scan- 
ning-lens assembly, a collector-lens as- 
sembly, a relay-lens assembly, and a 




Push-Pull Conversion Parts 

mask assembly. The scanning beam 
of light on the film is 230 mils long to 
cover adequately all types of sound 
tracks now in use. The collector and 



relay lenses transfer the modulated 
light to the mask assembly where one 
of three mask openings is placed in the 
light path, depending on the type of 
sound track being reproduced. The 
masks are selected by means of an ex- 
ternal three-position control knob. The 
light is then passed through separator 
lenses and reflected from a front-sur- 
faced mirror onto a dual-cathode photo- 
tube. 

The phototube coupler consists of a 
phototube mesh and a triode cathode 
follower which provides a 600-ohm out- 
put. An external switch control is in- 
cluded for connecting the dual-cathode 
of the phototube in parallel, for opera- 
tion with 100-mil standard sound track, 
or in push-pull, for operation with 100- 
mil or 200-mil push-pull sound track. 

In operation, the mask assembly con- 
trol is preset in the 100-mil standard, 
100-mil push-pull, or 200-mil push- 
pull position and the phototube 
coupler control is preset in the standard 
or push-pull position. No other opera- 
tional adjustment is required. 

The series P-200 push-pull conver- 
sion parts can be readily installed as 
they are designed to fit existing mount- 
ing details. 



214 



Journal of the 

Society of Motion Picture Engineers 

VOLUME 53 SEPTEMBER 1949 NUMBER 3 

PAGE 

Magnetic Recording in Motion Picture Techniques 

JOHN G. FRAYNE AND HALLEY WOLFE 217 

Recording Equipment Throughout the World R. E. WARN 236 

The Picture Splice as a Problem of Video Recording 

F. N. GILLETTE 242 

Navy Electronic Shutter Analyzer W. R. FRASER 256 

Simultaneous Determination of Elon and Hydroquinone in 

Photographic Developers 

HERBERT L. REES AND DON H. ANDERSON 268 

Lubrication of 16-Mm Films RALPH H. TALBOT 285 

Proposed American Standards 293 

66th Semiannual Convention 301 

Proposed New Constitution and Bylaws 304 

Committee Changes 308 

Reprinting Material from the JOURNAL 309 

Section Meetings 310 

Meetings of Other Societies 313 

Current Literature 314 

Book Reviews: 

"Elements of Sound Recording/' by John G. Frayne and 
Halley Wolfe 

Reviewed by Lloyd T. Goldsmith 315 

"Magnetic Recording," by S. J. Begun 

Reviewed by John G. Frayne 316 

New Products 317 

ARTHUR C. DOWNES HELEN M. STOTE NORWOOD L. SIMMONS 

Chairman Editor Chairman 

Board of Editors Papers Committee 

Subscription to nonmembers, $12.50 per annum; to members, $6.25 per annum, included in 
their annual membership dues; single copies, $1.50. Order from the Society's General Office. 
A discount of ten per cent is allowed to accredited agencies on orders for subscriptions and 
single copies. Published monthly at Easton, Pa., by the Society of Motion Picture Engineers, 
Inc. Publication Office, 20th & Northampton Sts., Easton. Pa. General and Editorial Office, 
342 Madison Ave., New York 17, N. Y. Entered as second-class matter January 15, 1930, 
at the Post Office at Easton, Pa., under the Act of March 3, 1879. 

Copyright, 1949, by the Society of Motion Picture Engineers, Inc. Permission to republish 
material from the JOURNAL must be obtained in writing from the General Office of the Society. 
Copyright under International Copyright Convention and Pan-American Convention. The 
Society is not responsible for statements of authors or contributors. 



Society of 

Motion Picture Engineers 

342 MADISON AVENUE NEW YORK 17, N. Y. TEL. Mu 2-2185 
BOYCE NEMEC . . . EXECUTIVE SECRETARY 

OFFICERS 

1949-1950 



PRESIDENT 
Earl I. Sponable 
460 W. 54 St. 
New York 19, N. Y. 

EXECUTIVE 
VICE-PRESIDENT 
Peter Mole 

941 N. Sycamore Ave. 
Hollywood 38, Calif. 



PAST-PRESIDENT 
Loren L. Ryder 
5451 Marathon St. 
Hollywood 38, Calif. 

EDITORIAL 
VICE-PRESIDENT 
Clyde R. Keith 
120 Broadway 
New York 5, N. Y. 



SECRETARY 
Robert M. Corbin 
343 State St. 
Rochester 4, N. Y. 

CONVENTION 
VICE-PRESIDENT 
William C. Kunzmann 
Box 6087 
Cleveland 1, Ohio 



1948-1949 



ENGINEERING 
VICE-PRESIDENT 
John A. Maurer 
37-0131 St. 
Long Island City 1, N. Y. 



TREASURER 
Ralph B. Austrian 
25 W. 54 St. 
New York 19, N. Y. 



1949 

FINANCIAL 
VICE-PRESIDENT 
David B. Joy 
30 E. 42 St. 
New York 17, N. Y. 



1948-1949 

Alan W. Cook 
4 Druid PI. 
Binghamton, N. Y. 



Lloyd T. Goldsmith 
Warner Brothers 
Burbank, Calif. 



Paul J. Larsen 
508 S. Tulane St. 
Albuquerque, N. M. 



Gordon E. Sawyer 
857 N. Martel Ave. 
Hollywood 46, Calif. 



Governors 
1949 

James Frank, Jr. 
1310 Peachtree Battle 

Ave., N. W. 
Atlanta, Ga. 

William B. Lodge 
485 Madison Ave. 
New York 22, N. Y. 

William H. Rivers 
342 Madison Ave. 
New York 17, N. Y. 

Sidney P. Solow 
959 Seward St. 
Hollywood 38, Calif. 

R. T. Van Niman 
4431 W. Lake St. 
Chicago 24, 111. 



1949-1950 

Herbert Barnett 
Manville Lane 
Pleasantville, N. Y. 



Fred T. Bowditch 
Box 6087 
Cleveland 1, Ohio 



Kenneth F. Morgan 
6601 Romaine St. 
Los Angeles 38, Calif. 



Norwood L. Simmons 
6706 Santa Monica Blvd. 
Hollywood 38, Calif. 



Magnetic Recording in Motion 
Picture Techniques* 

BY JOHN G. FRAYNE AND HALLEY WOLFE 
WESTERN ELECTRIC COMPANY, HOLLYWOOD 38, CALIFORNIA 

Summary Development of magnetic recording at the Bell Telephone 
Laboratories is described with the application of such facilities to Western 
Electric recording and reproducing systems. A method of driving 35-mm 
magnetic film with a flutter content not greater than 0.1 per cent is de- 
scribed, as is a multigap erasing head. . 

INTRODUCTION 

\ LTHOUGH THE PRINCIPLES of magnetic recording on a steel wire 
V*- were first demonstrated by Poulsen in 1898, this method of 
recording has had little if any application to practical recording 
techniques until the past few years. The reasons for the half -century 
delay between discovery of the method and its successful application 
to broadcasting and sound motion picture techniques may be at- 
tributed partly to a lack of understanding of the basic process, and 
partly to the fact that the quality of sound reproduced from the early 
devices left much to be desired. 

During the late twenties research into the possibilities of obtaining 
high-quality sound from the magnetic medium was begun at the Bell 
Telephone Laboratories. This work led to the production of the 
Mirrophone magnetic recorder in 1941 which may be said to be the 
first high-quality magnetic recorder made available to the public. 
Although many of the principles employed in the Mirrophone have 
given way to later developments in the magnetic-recording art, they 
are still of interest in tracing the gradual improvements in this 
method of recording. The technique developed by Hickman at the 
Bell Telephone Laboratories and incorporated in the Mirrophone 
employed the perpendicular type of magnetization in which the ele- 
mentary magnets are at right angles to the line of travel of the 
medium, which was a special steel-alloy tape known as Vicalloy. 

DIRECT-CURRENT BIAS 

In order to circumvent the inherent distortion in the magnetic- 
recording characteristic as exemplified in Fig. 1, showing relative 

* Presented April 8, 1949, at the SMPE Convention in New York. 

SEPTEMBER, 1949 JOURNAL OF THE SMPE VOLUME 53 217 



218 



FRAYNE AND WOLFE 



September 



reman ent induction and magnetizing force, Hickman 1 employed a 
direct-current saturation erase and a negative direct-current biasing 
field, as illustrated in Fig. 2. His explanation of the recording process 
is as follows. The tape, on passing between the direct-current eras- 
ing pole pieces, is magnetized to the saturation point P on curve A. 
On leaving the erase gap, the magnetic induction drops along the 
curve B to R. On passing between the recording pole pieces, a nega- 
tive biasing flux brings the material to a point N. As the medium 
passes out from between the recording pole pieces, the residual induc- 
tion will change from N to which is a substantially neutral con- 
dition. If an alternating-current signal is applied between A and B 
on the hysteresis curve while the medium is passing through the gap 



Fig. 1 Curve showing relation- 
ship between remanent induction 
and magnetizing force. 




Fig. 2 Curves illustrating process of 
recording with direct-current bias. 



the residual induction will vary between A' and B'. A more elabo- 
rate explanation of this recording process is given by Wooldridge. 2 

This method makes it possible to record over a large portion of the 
magnetization curve without appreciable distortion. At the same 
time the magnetic noise is kept at the minimum by virtue of working 
the tape about an essentially demagnetized condition. 

With the Mirrophone recorder operating at a tape speed of 16 
inches per second, the maximum signal-to-noise ratio of 38 decibels 
was obtained, with a substantially uniform equalized frequency re- 
sponse up to 8000 cycles. The quality and signal-to-noise ratio of 
these recordings were comparable to that of standard optical sound 
tracks, and at 8 inches per second the quality was considered satis- 
factory for dialog. 



1949 



MAGNETIC RECORDING 



ALTERNATING-CURRENT BIAS 



219 



Although the direct-current-bias method was capable of giving 
fairly good quality, the quality was not sufficiently outstanding nor 
was the signal-to-noise ratio sufficiently great to capture the serious 
attention of the sound-recording industry. Consequently, research 
continued at the Bell Telephone Laboratories which culminated 
in the successful application of high-frequency bias and high-fre- 
quency-erasing methods instead of the direct-current methods 
generally employed up to that time. While a high-frequency-bias 
method was disclosed in U. S. Patent 1,640,881, issued in 1927 to 




Fig. 3 Recording characteristics using alternating-current 
bias. 

W. L. Carlson and G. W. Carpenter of the General Electric Company, 
its first known application to magnetic recording was at the demon- 
stration of stereophonic-recording methods at the New York World's 
Fair in 1938 by the American Telephone and Telegraph Company. 
U. S. Patent 2,235,132 was issued in 1940 to D. E. Wooldridge of the 
Bell Telephone Laboratories covering new and improved techniques 
in applying the erasing and biasing high-frequency fields. The 
method disclosed by Wooldridge calling for the mounting of erasing 
and recording heads on the same recording unit with a high frequency 
applied to each unit is followed in most modern magnetic-recorder 
designs. 



220 FRAYNE AND WOLFE September 

Although the complete theory of the high-frequency-bias method is 
complex, 3 a somewhat simplified explanation is given here. In 
endeavoring to picture the process, it is convenient to think of the 
recording material as passing through an intermediate stage just 
after leaving the recording field but before demagnetization sets in. 
In this stage the relation between residual magnetization and maxi- 
mum magnetizing force in the gap is expressed by curve abed in 
Fig. 3. A group of bias-frequency waves with superimposed audio- 
frequency wave is shown as an impressed magnetizing force around the 
origin 0. Assuming that the curve abed represents the recording 
characteristic, then the maximum values of B r , the residual magneti- 
zation, may be traced as shown in the figure. After the medium 
leaves the recording gap almost complete demagnetization of the 
bias frequencies results, leaving a net induction which is the difference 
between the positive and negative halves of the bias waves. Thus 
the remaining magnetization is shown by the curve ef of Fig. 3. It will 
be noted that for a zero value of audio signal* the medium is almost 
completely demagnetized with resulting low noise output from the 
tape. Further, since the audio signal is transferred to the linear 
position b and c of the characteristic curve, the distortion of the audio 
signal is low. 

THE MAGNETOPHON 

New impetus to more extended use of the magnetic recording 
medium was given by the discovery by the Allies in Germany at the 
close of World War II of the Magnetophon, 4 which had been widely 
adopted by the German broadcasting system. This machine utilized 
a plastic tape with either an impregnated or coated layer of magnetic 
iron-oxide powder with particle diameters less than 1 micron. With 
longitudinal-type magnetization and operating at a speed of 30 
inches per second, a signal-to-noise ratio of about 60 decibels was 
obtained and an equalized flat response to 15,000 cycles was claimed. 
The sound quality from the Magnetophon was so superior to that of 
all previous magnetic recorders, that it immediately appeared in- 
evitable that this improved medium would eventually be extended 
to all fields of sound recording. 

The tapes employed in the Magnetophon and later in domestic 
magnetic recorders were J /4 mcn wide and 2 to 3 mils thick. Without 
sprocket holes the tape speed could not be maintained in exact 
synchronism with a motion picture on perforated film unless some 



1949 



MAGNETIC RECORDING 



221 



external form of speed control was employed. The development 
of a perforated film (35 mm or 16 mm) was therefore necessary before 
the new medium could be introduced to the motion picture field. 
As the result of considerable effort expended by certain companies 
such as the Minnesota Mining and Manufacturing Company and 
the du Pont Company, satisfactory magnetic iron-oxide emulsions 
on standard 35-mm film, mounted on either nitrate or safety base, 
have been produced. 







Fig. 4 Western Electric RA-1231 Type magnetic recorder, in which control 
panel has been substituted for optical components. 

MOTION PICTURE ADAPTATION 

To adapt magnetic recording for motion picture use it is essential 
that the quality obtained from the 35-mm magnetic film be at least 
equal in every respect to that obtained from optical sound tracks. 
This means that frequency response, signal-to-noise, and flutter 
performance must be at least comparable. The Magnetophon expe- 
rience indicated that the first two of these conditions should easily 
be met even at the lower motion picture speed of 18 inches per second. 
The flutter problem presented in pulling a fairly stiff 35-mm film 
over a fixed recording head required careful consideration in order to 






222 



FRAYNE AND WOLFE 



September 



match the almost flutter-free performance of modern sound recorders 
and reproducers. As discussed later in this paper this problem has 
been completely solved. 

Before the studio can readily apply magnetic recording to produc- 
tion problems it is necessary to have magnetic-reproduction facilities 
throughout the studio comparable to those now afforded for optical 
sound tracks. Thus, provision must be made for reviewing the daily 
magnetic recordings in synchronism with the action. This means that 
review-room projectors must be equipped for magnetic reproduction 




Fig. 5 Western Electric RA-1231 Type magnetic recorder, in which 
optical facilities are retained. 

without impairing their ability to reproduce standard film sound 
tracks. Also, editing machines must be provided to aid in cutting 
and assembling the component magnetic tracks for re-recording to 
the release optical track. Finally, re-recording machines must be 
modified to reproduce the magnetic tracks with the same degree 
of excellence these machines afford for existing sound tracks. 

As will be shown later in this paper, the Western Electric Company 
is making available magnetic modification parts for its RA-1231 
series of film recording machines. It is also providing magnetic- 
reproducing facilities for its RA-1251 series of re-recording machines 



9 



MAGNETIC RECORDING 



223 



as well as for the RA-1435 theater-type of reproducers for review- 
room reproduction of magnetic recordings. It is also co-operating 
to provide facilities for editing and cutting magnetic sound tracks. 

RECORDER 

The magnetic recorder to be described utilizes the Western Electric 
RA-1231 photographic film recorder as a basis, with a number of 
added or substituted conversion parts. The standard speed of 
18 inches per second has been retained. 

Two versions of this recorder have been developed to date. In 
one, the optical components in the light-modulator compartment are 



PULL -DOWN 
SPROCKET 



ERASING HEAD 
IDLER ROLLER- 



RECORDING 
DRUM 



RECORDING - 
HEAD 



SHIELD -> 




SHIELD 



REPRODUCING- 

[MONITOR]HEAD 
Fig. 6 Magnetic-recorder film path. 

removed, and a control panel and a number of electrical items are 
substituted for them. This recorder is shown in Fig. 4. In the 
other version the optical facilities are retained, the control circuits 
being mounted external to the recorder (Fig. 5). In this latter ver- 
sion the recorder can be rapidly converted for use with either the 
magnetic or the photographic medium. 

In both variations of the recorder, the general layout of heads and 
other components in the film path is the same and is shown in Fig. 6. 
When an erasing head is used it is mounted to contact the incoming 
magnet c film at the short loop between the pulldown sprocket and 
the first (upper) filter arm roller. The recording head is mounted 
on a damped supporting arm, and it contacts the magnetic coating 



224 



FRAYNE AND WOLFE 



September 



FILM 



,- RECORDING 
DRUM 



-RECORDING 
HEAD 



SECTION A-A 



FILM 



GAP 



MAGNETIC 
COATING 

RECORDING 



at the recording drum. The reproducing or monitor head is mounted 
above the tight loop following the recording drum, between the drum 
and the second (lower) idler roller. Head adjustments are provided 
for setting track position, for properly positioning the gaps relative 
to the film loops passing over them, and for setting azimuth of the 
recording and reproducing heads. 

The manner of mounting the recording head is indicated in Fig. 7. 
A recording drum somewhat narrower than that for optical recording 
is employed, the film thus overhanging about 5 / 8 inch on the out- 
board side, as shown. The film is threaded so that the magnetic 

coating is on the inside of the 
loop in contact with the surface 
of the drum. The gap of the 
recording head contacts the in- 
side of the overhanging loop near 
the edge of the drum. The re- 
cording head is flexibly mounted 
on an arm that is pivoted at a 
point directly below the record- 
ing gap. A spring attached to 
this arm supplies sufficient force 
to hold the recording gap against 
the film, the force of the spring 
being easily adjustable. Viscous 
damping applied to the mount- 
ing arm attenuates any vibratory 
motion imparted to it. 

This system of film propul- 
sion over the recording head gives excellent performance with 
regard to freedom from flutter and amplitude modulation because 
it utilizes the same point of translation that has previously been 
determined as giving the optimum performance in optical record- 
ing. 5 When the force on the arm is properly adjusted the uni- 
formity of film motion is comparable to that obtained in optical 
recording in the same recording machine. This is largely due to 
the fact that the film .loop, being rigidly supported over most of 
its width, is not so subject to "polygoning" at the film perfora- 
tions. Furthermore, the head automatically assumes the proper 
position when the film is threaded, any wear on the head being com- 
pensated by a slight motion of the arm. Measurements of flutter 




RECORDING-' 
HEAD 



-PIVOT 

SPRING- 

Fig. 7 Method of mounting 
magnetic-recording head. 



1949 MAGNETIC RECORDING 225 

(summarized in a following section) confirm the superiority, partic- 
ularly with regard to 96-cycle flutter, of this method over the usual 
method whereby the film is pulled over the head in an unsupported 
loop. 

The undesirable 96-cycle amplitude and frequency modulation 
which are introduced in the region near the sprocket holes by the 
"polygoning" effect may be eliminated by moving the track position 
away from the sprocket holes. Since there seems to be no reason for 
maintaining optical track position on original magnetic records, a 
centerline position of 0.450 inch from the edge of the film has been 
tentatively established. The track width has been set at 0.250 inch 
leaving the inside edge of the track 0.136 inch from the inside edge of 
the sprocket holes. Adjustments are provided for moving the center- 
line when some other position is desired. 

The monitoring or reproducing head picks up the signal about 
0.4 second after it has been recorded. Because of the more unfavor- 
able position of the reproducing head in the film path, the reproduced 
signal has more 96-cycle flutter than the recorded signal. However, 
the quality is entirely adequate for monitoring purposes, and flutter- 
free performance comparable to that at the recording position is 
obtained in the reproducer (described below) in which the same type 
of drum-controlled motion is employed. Also, if desired, the. re- 
corder itself can be employed as a reproducer, the recording head then 
acting as a reproducing head. 

MAGNETIC-HEAD DESIGN 

The magnetic pole pieces for the heads are constructed of circular 
laminations of Permalloy, tightly held in the halves of a divided, 
circular brass ring that, in turn, is positively aligned by an accurately 
made clamping fixture. An exploded view of such a head is shown 
in Fig. 8. Coils are wound on molded coil forms that slip over the 
pole pieces. Recording and reproducing gaps are each 0.0005 inch 
wide and 0.25 inch long, and are formed of shims of beryllium-copper 
alloy placed between the ground ends of the pole pieces. 

The erasing head differs from the conventional type in that two 
gaps are used, so that an element of the recording medium is subjected 
to two successive erasing processes in passing over the head. These 
gaps are 4 mils wide and are spaced 6 mils apart. They are formed 
by inserting (between the pole pieces) a three-layer "sandwich" 
consisting of two shims of 6-mil nonconducting material separated 



226 FRAYNE AND WOLFE September 

by a Permalloy lamination. By thus applying an erasing field to 
the medium, allowing the latter to relax to the neutral state, then 
applying a second erasing field, very effective erasure is obtained 
with low-power dissipation in the head. Even with magnetic 
materials that are most difficult to erase, fully modulated signals 
have been completely removed. This has been accomplished with 
power values sufficiently low so that the head can be operated con- 
tinuously without any significant temperature rise; stationary 
film can be kept in contact with the pole piece indefinitely without 
injury. 



LAMINATION- 
RETAINER 




LAMINATIONS 



COIL FORM 



Fig. 8 Magnetic-recording head, exploded view 
of core details. 

Each of the magnetic heads is enclosed by a Permalloy case for 
shielding, and in addition, external Permalloy shields in the form 
of plates are mounted adjacent to the recording and reproducing 
heads to provide further shielding of the exposed regions near the gaps. 

RECORDING TRANSMISSION SYSTEM AND CONTROLS 

The magnetic-recording channel includes all facilities required for 
recording and monitoring the signal output from an RA-1288 mixer, 
and for reproducing the signal after it is recorded. The channel can 
also be bridged across a normal bridging line. A block schematic of 
the complete system is shown in Fig. 9. The amplifiers, the bias 
oscillator, the power supplies, and various equalizers and other net- 
works, are mounted on a single rack, whereas all the frequently 
operated controls are located on a single panel. 



1949 



MAGNETIC RECORDING 



227 



The main elements of the audio-frequency portion of th& recording 
circuit are the two amplifiers, adjustable attenuator, pre-equalizers, 
and volume indicator. One oscillator supplies both bias current 
to the recording head and erasing current to the erasing head. This 





oscillator is mounted in the rack with its separate power supply, its 
output being connected to the recorder circuits through a coaxial 
cable. The oscillator includes a resistance-capacitance-type circuit 
of high stability and an output amplifier with a push-pull circuit in 



228 FRAYNE AND WOLFE September 

order to reduce to a minimum the even harmonics of the bias fre- 
quency. A sharply tuned filter is located in the output to reduce 
further the harmonics and to prevent any audio-frequency noise in 
the oscillator from reaching the recording head. An oscillator 
frequency of 60 kilocycles is employed. This frequency is high 
enough so that any appreciable intermodulation products between 
the signal and the bias frequency are above the audio-frequency range. 

The monitor system includes all amplifiers and networks required 
for delivering a properly equalized monitoring signal either from the 
recording head current (direct monitor) or from the recorded material 
on the film (film monitor). Equalizers in the film-monitor circuit 
include a 6-decibel-per-octave shelf equalizer to compensate for the 
low-frequency droop inherent in magnetic recording and a post- 
equalizer. A "film-loss" equalizer to compensate for the high-fre- 
quency film loss is optional. The monitor signal is delivered at 
headset level to a convenient jack and to a plug outlet for trans- 
mission to the mixer, or other remote location. 

As previously indicated, the switches and other equipment for 
normal recording operations are mounted either on a small panel in 
the recorder, or externally in the version that retains the optical- 
recording facilities. A meter is provided for indicating bias and 
erasing current; normally this indicates bias current, but a nonlock- 
ing switch can be pressed to read erasing current. A bias-current 
adjustment is provided. Erasing current is controlled at the rack 
by means of an over-all oscillator output control. Additional con- 
trols are -"on-off" switches for both bias and erasing current, a direct- 
monitor or film-monitor selector switch, a monitor volume control, 
and three-position selector switch that can be set for "signal-off," 
"record," or "reproduce." In the "reproduce" position the recording 
head is connected for reproducing, and oscillation of the bias oscillator 
is stopped in order to eliminate danger of erasing the record. 

In locations where powerful permanent magnetic fields are present, 
as, for example, near magnetized structural steel, the introduction 
of appreciable second-harmonic distortion and noise in the record is 
possible, because of the resulting polarization of the recording head. 
To eliminate this difficulty, a source of direct current to the recording- 
head has been provided in the oscillator. The current can be ad- 
justed and its value can be read on a microammeter at the oscillator; 
a reversing switch is provided to reverse the polarity of the recording 
head. Thus, any polarization in the recording head can be canceled. 



1949 



MAGNETIC RECORDING 



229 



Under most circumstances it is not necessary to utilize this feature, 
but it is available if needed. 

PEE- AND POSTEQUALIZATION 

Pre- and postequalization are employed to increase the signal- 
to-noise ratio. Although the basic theory of operation of this method 
of noise reduction is identical whether it is applied to magnetic or to 
photographic recording, the magnetic medium requires somewhat 
different equalization for optimum results. Whereas with film 
recording the noise energy is predominantly in the high frequencies, 



u -flO 

1+5 
to 

Ul 

K 
Id 

H - 5 
-10 



PRE 



50 



100 



200 500 1000 2000 

FREQUENCY IN CYCLES PER SECOND 



5000 



10000 



Fig. 10 Magnetic-recording pre-equalization curve. 

with magnetic recording, mainly because of the 6-decibel-per-octave 
equalization, the low frequencies usually contain the greater portion 
of the noise energy. Therefore, in addition to the normal photo- 
graphic-type high-frequency equalization, some equalization is 
applied to the frequencies below 250 cycles. The resulting over-all 
pre-equalization characteristic is shown in Fig. 10; the postequaliza- 
tion is, of course, complementary to this curve, as shown. 

PERFORMANCE 

Flutter measurements indicate that the method of film propulsion 
used in this recorder, in which the recording head is located at the 
recording drum, produces a record that is somewhat better than a 



230 



FRAYNE AND WOLFE 



September 



print in the photographic process. The total flutter is about 0.1 
per cent, mainly in the 80- to 130-cycle band. Since the flutter 
index is relatively low for this condition, the effects on sound quality 
are naudible. 6 At the monitoring or reproducing-head position, 
the well-known detrimental effects of free-loop and curved-gate 
scanning are evident, the total flutter being about three times that 
of the recording position. Here again the 80- to 130-cycle band pre- 
dominates. At both positions the low-frequency flutter performance 
is excellent. No 96-cycle amplitude modulation can be seen on the 
envelope of a recorded signal viewed on an oscilloscope. 



+ 5 



s 

z 

UJ , 

v>- 5 
fc-IO 



-; 



20 



50 



100 



5000 



10000 



200 500 1000 2000 

FREQUENCY IN CYCLES PER SECOND 

Fig. 11 Magnetic-system frequency characteristic. 

The frequency response of the unequalized system is shown by 
curve A of Fig. 11. Equalization is added in reproduction to produce 
the characteristics indicated by curve B, and ordinarily a 40- cycle 
high-pass filter is also included. With music, excellent results have 
been obtained with this equalization only; however, the high signal- 
to-noise ratio will permit raising of the relative level of the frequenc'es 
beyond the peak response to produce an over-all response that is flat 
to about 10 kilocycles. 

In determining the signal-to-noise ratio, the overload level was 
arbitrarily taken as that level at which the third-harmonic distortion 
is 2.5 per cent at 400 cycles. This frequency was chosen because it is 



1949 



MAGNETIC RECORDING 



231 



near the region of maximum energy in the spectral-energy-distribu- 
tion curve. The second harmonic is so low in level that it may be 
neglected. This figure for overload has some justification, since it 
has been found that excellent recordings of all types of material can 
be made with this as the peak recording level. On this basis, a sig- 
nal-to-noise ratio of more than 55 decibels can be obtained when the 
frequency characteristic given by curve B (Fig. 11) is employed in 
addition to the usual 40-cycle high-pass filter. With pre- and post- 
equalization, the effective ratio lies between 58 and 62 decibels. 

MAGNETIC RE-RECORDER 

The magnetic re-recorder, like the recorder, is made by applying 
a number of conversion parts to a standard film machine. The 
Western Electric RA-1251- 
B re-recorder is the basic 
unit, to which are added 
mechanical and electrical 
items needed to reproduce 
the magnetic sound track. 
One method of scanning 
the track is accomplished 
at the scanner drum in a 
manner analogous to that 
utilized in the recorder. In 
the film path, the conver- 
sion involves removing the 
lens-and-prism assembly, 
replacing the scanner drum 




and installing the reproduc- 



Fig. 12 Magnetic-re-recorder film path. 

ing head and its movable, damped support and its shielding struc- 
ture. The resulting film path is shown in Fig. 12. 

In another version of the re-recorder, the reproducing head replaces 
the roller in the film path just beyond the scanner drum. Thus, in 
this model optical facilities are retained, and the machine can be used 
to play either photographic or magnetic film. 

Removing the circuit items not needed in magnetic reproducing, 
such as the phototube amplifier and the lamp-control equipment, 
leaves ample room for the magnetic-transmission system. This 
system, shown in block schematic in Fig. 13, includes RA-1214-D 
amplifiers, high- and low-frequency equalizers, and keys for switching 



232 FRAYNE AND WOLFE September 

them in or out of the circuit separately, the 6-decibel-per-octave 
reproducing equalizer, adjustable film-loss equalizer, gain control, and 
power supply. The output signal from the re-recorder has a nominal 
level of +10 dbm* when the gain is set at maximum. 

Performance of this re-recorder is comparable in every way to that 
of the recording system as given above. When drum scanning is 
employed, the performance with regard to amplitude modulation and 
flutter is indentical to that of the recorder at the recording-drum posi- 
tion. In the other version, performance is comparable to that 
at the monitor position hi the recorder. The figures of signal-to- 
noise ratio given for the recorder also apply to the re-recorder. 

REVIEW-ROOM FACILITIES 

Since the studio review room must be capable of reproducing double 
film for dailies and composite film for release, it is necessary to provide 
facilities for magnetic reproduction as well as standard optical-track 
reproduction from composite prints. This has been done to date on 
the RA-1435 theater-type sound reproducer as illustrated 7 in Fig. 14. 
It will be noted that the standard optical-reproducing facilities are 
unchanged. In order to accommodate the magnetic-reproducing 
head, it has been necessary to move the lower idler roller about 1 
inch to the right, the resulting film path being as shown in the figure. 
The flutter performance of this machine for magnetic reproduction 
shows a slightly h gher 96-cycle rate than for optical reproduction. 
However, because of the favorable flutter index at this high rate of 
flutter frequency, the quality of sound is not noticeably impaired. 

Space requirements in the soundhead make it necessary to mount 
the magnetic-reproducing head outside the film loop rather than inside 
the loop as used on the RA-1231 recorder and RA-1251 re-recorder. 
This puts the emulsion in he same position as in the optically recorded 
films and is desirable in a machine which is used interchangeably for 
magnetic and optical recordings. The head is on a retractable 
mounting controlled by a rotatable knob at the lower left so that it is 
removed from contact w T ith the film when photographic tracks are used. 

CONCLUSION 

A magnetic recorder has been described in which suitable recording, 
monitoring, and erasing facilities are provided. Magnetic sound 
tracks made in this machine at the standard speed of 18 inches per 
second are practically free from flutter and show an excellent 
* Decibels with respect to 0.001 watt. 



1949 



MAGNETIC RECORDING 



233 



frequency response for sound-picture reproduction purposes. A 
standard film re-recording machine has been converted for reproducing 
magnetic sound tracks with a high degree of fidelity. In addition a 
standard theater-type sound reproducer has been modified to provide 
reproduction from either optical or magnetic sound tracks. Re- 
cordings of music and dialog made on this system show an excellence 




Fig. 14 Western Electric RA-1435 theater sound 
reproducer, showing facilities for reproducing 
magnetic track. 

of quality unsurpassed in any previously known recording system. 
The complete absence of background noise lends an air of reality to 
the reproduced sound, making it indistinguishable from direct 
monitoring of the original pickup on the stage. 

With the facilities described in this paper, the sound-recording 
engineer should be able to begin active adaptation of magnetic re- 
cording to his everyday production activities. Further, he should be 
able to carry on the magnetic program through all the various stages 
of editing and re-recording, up to the release negative which must for 



234 FRAYNE AND WOLFE September 

the present perforce be an optical sound track for theater reproduct on 
purposes. 

REFERENCES 

(1) C. N. Hickman, "Sound recording on magnetic tape," Bell Sys. Tech. 
Jour., vol. 16, p. 165; April, 1937. 

(2) D. E. Wooldridge, "Signal and noise levels in magnetic tape recording," 
Trans. A.I.E.E., vol. 65, p. 343; June, 1946. 

(3) W. W. Wetzel, "Review of the present status of magnetic recording theory," 
Audio Eng., p. 12; December, 1947. 

(4) Publication No. 60899, Office of Technical Services, Department of Com- 
merce, Washington, D. C. 

(5) C. C. Davis, "An improved film-drive filter mechanism," J. Soc. Mot. Pict. 
Eng., vol. 46, pp. 454-465; June, 1946. 

(6) SMPE Committee on Sound, "Proposed standard specifications for flutter 
or wow as related to sound records," /. Soc. Mot. Pict. Eng., vol. 49, pp. 147- 
160; August, 1947. 

(7) G. R. Crane, "Theater reproducer for double-width push-pull operation," 
J. Soc. Mot. Pict. Eng., vol. 52, pp. 657-662; June, 1949. 

DISCUSSION 

MR. J. E. AIKEN: What are your decisions on the use of perforated material? 
We take it for granted, but at the same time we would like to know what the re- 
sults are, particularly when the drive is synchronized for a nonperforated tape, 
and particularly if you can discuss the effects on synchronization of any heating 
effect that might take place at the moment of recording. 

DR. JOHN G. FRAYNE: So far as the motion picture industry is concerned, it is 
accustomed to handling film with sprocket holes, using the standard well-known 
method of keeping exact synchronism with a synchronous or interlock drive 
system. The quarter-inch-tape machines have been used in some studios for 
various purposes with very good results, but mostly for playback purposes, re- 
hearsals, and things of that nature. When one tries to record on tape without 
sprocket holes and to associate that with the picture, the slippage is too great 
for present standards of synchronization. That is not my conclusion; it is the 
conclusion of people in the industry. 

With regard to stretching of the tape caused by heating, I have heard of that 
defect but I cannot vouch for it At this time sprocket holes, for either \7 l /<r or 
35-mm, are definitely indicated for motion picture studios. 

MR. LEON S. BECKER: Dr. Frayne, do you have any figures that are available 
on intermodulation? 

DR. FRAYNE: No. The accepted method of measuring intermodulation is 
doubtful because of the equalization which we have to apply in reproduction. 
Take, for example, the 60- and 1000-cycle or 60- and 2000-cycle test which is 
made in ordinary intermodulation: the 60-cycle component is reproduced some 
20 decibels higher on equalized setups than the 1000; so it completely throws 
the balance of 60 and 1000 out as far as analysis is concerned. The recording 
you heard here was made so the film showed a maximum third harmonic of 2Va 
per cent and a second harmonic of less than 1 /2 of a per cent, which should be 
about 10 per cent intermodulation. The method of measuring distortion on 



1949 MAGNETIC RECORDING 235 

magnetic is still, I would say, in the development stage. Undoubtedly, some 
peculiar form of distortion measurement will materialize. So far, the third har- 
monic seems to be a very good way of measuring distortion in magnetic recording. 

MR. BECKER: Were the first two samples radio pickups? 

DR. FRAYNE: Yes. 

MR. BECKER: I felt that there was a considerable amount of distortion of some 
type, and in the last sample, which was a vocal, I wanted to hear an orchestra 
combination rather than a vocal and organ. I could not tell whether the distor- 
tion might have been caused by the radio transmission. 

DR. FRAYNE : Some distortion undoubtedly was in the over-all system. This 
was reproduced over a system flat to somewhat above 9000 cycles. If this 
had been reproduced over the so-called Research Council characteristic, I think 
you would not have noticed any appreciable distortion. 

MR. BECKER: Has Western Electric developed any special editing equipment? 

DR. FRAYNE: We are co-operating with the Moviola Company at the present 
time, and I do not know just how far that has gone. 

MR. BECKER: Does the contact of the recording head contribute to any ap- 
preciable degree to increased flutter content? 

DR. FRAYNE : It does to a certain extent. In the old theater days, we had 
straight gates. Then we went to curved gates. Finally, we went to rotary gates. 
This is a compromise between rotary and curved gates. The motion of the film 
at the point of contact is dominated partially by the rotary motion of the drum 
and partially by the friction on the gate, but the flutter values I gave are com- 
parable to that in film and better than a good print. 

MR. BECKER: In other words, that figure 0.07 was the magnetic flutter? 

DR. FRAYNE: Yes. 

MR. GORDON CHAMBERS: I hope that the terminology Dr. Frayne used this 
morning will not catch on, and that the term "optical" will not come to be synony- 
mous with photographic. He spoke this morning of an optical contact print, and 
I do hope that in Hollywood photographic recording will not be described as opti- 
cal recording. 

DR. FRAYNE : I am afraid it is too late to change the terminology now. It is 
already started. 

MR. CHAMBERS: It is going to lead to considerable confusion for some time to 
come because we do have optical work as well as photographic. 

MR. KENNETH C. GOODMAN: Has any thought been given to the tie-in of this 
equipment with 16-mm films that will be produced? In the Midwest, we shall 
have to produce many of our films for use on television. How can we synchronize 
it? 

DR. FRAYNE: Is your television speed 7.2 inches in seconds? Is it a standard 
16-mm speed? 

MR. GOODMAN: Yes. 

DR. FRAYNE: Then there is no problem any more than in 35-mm. This little 
recorder over here can be equipped for 16 as well as 35. You just have to 
change the plates mounting the drive mechanism in there. Of course you will 
have to change the head mountings. 

MR. GOODMAN: Is the 16-mm machine available? 

DR. FRAYNE: If anyone wants one we shall be more than happy to supply it. 



Recording Equipment 
Throughout the World* 

BY R. E. WARN 

WESTREX CORPORATION, NEW YORK 11, NEW YORK 



Summary The paper presents a survey of recording outside the United 
States of America, contrasting the problems of these studios with those of 
Hollywood. The equipment and service organizations developed to meet 
the needs of these studios are described. 

PHE FILM INDUSTRY has long looked upon Hollywood and London 
-^- as the focal points of recording activities, so much so, in fact, 
that it is often felt that these two centers embrace virtually all of the 
recording activities in the world. Actually, extensive film recording 
is today being carried on in practically every country of significance 
around the globe. All told there are approximately 200 studios 
producing 35-mm films outside of the United States. Most of these 
studios are small by Hollywood standards. However, the pride of 
local production is a very potent box-office reason for the existence 
of many of these units and, in addition, many governments have 
encouraged their establishment. 

It will assist in understanding the problems of these studios to 
to consider typical cases. From the standpoint of size, facilities, 
geographic location, climatic and working conditions, they cover a 
wide range. For example, Fig. 1 shows the Azteca Studio at Mexico 
City which, until recently, had 23 stages and 7 recording channels. 
In June, 1948, fire destroyed six of the stages but even without them 
Azteca justifies the classification of a large studio. 

An example of one of the smaller studio buildings is that of Com- 
monwealth Films in Sydney, Australia. The activities of this studio 
are housed in one building approximately 150 feet long by 50 feet 
wide. In this building there are the offices, dressing rooms, recording 
rooms, sound stage, carpenter shop, and property-storage facilities. 

The Sri Krung Studio at Bangkok, Siam, is an example of a studio 
catering to a very small market. Its pictures are produced in the 
Siamese language and distribution is effectively limited to the 100 

* Presented October 26, 1948, at the SMPE Convention in Washington. 
236 SEPTEMBER, 1949 JOURNAL OF THE SMPE VOLUME 53 



RECORDING EQUIPMENT 



237 



, h ,. 



,ters in Siam. As a market this is approximately equivalent to 
the city of Washington, D. C. 

The operating problems of these studios differ considerably from 
those of a Hollywood studio. The relatively small market to which 
they cater forces them to be highly versatile in policy, personnel, and 
equipment. In addition to features, many make commercials and 
documentaries, some produce newsreels, and some operate in both 
the 35-mm and 16-mm fields. Foreign pictures average a great deal 
higher percentage of location recording than Hollywood. In fact, 
in the smaller studios the greater portion of the picture is usually shot 
on location. 




Fig. 1 Azteca Studio, Mexico City. 

Dubbing is a highly important activity of many of these studios. 
For example, Fono Roma in Rome dubs an average of fifteen features 
per month, while Emelco in Buenos Aires dubbed one million feet of 
film on one recorder in the first seven months of its use. In some 
cases subtitles are used but this practice is diminishing. In many of 
the dubbing operations a print is provided by Hollywood which 
includes all sound except the dialog. In such cases it is particularly 
important that the quality of the sound provided by Hollywood be 
matched when the dialog is added. 

Studio personnel have to be able to do a little of everything as there 
is not sufficient budget or volume of all types of activities to warrant 
specialists for every job. In many of the small studios there is only 



238 WARN September 

one recording channel and it must serve on location, in the studio, 
and for scoring and re-recording, sometimes for both 35-mm and 16- 
mm work. The equipment must be very portable and there must be 
no lost time because of technical difficulties due to mobility. These 
studios need quality comparable with Hollywood but the equipment 
must, in general, be more portable, more versatile, less expensive, 
and capable of producing good results with a minimum of attention. 

The cost of local talent and technicians in these studios is a great 
deal less than in Hollywood. As an example of an extreme case, the 
star in one Malayan picture produced just before the war received the 
equivalent of $5.00 per day. This trend to lower costs is reversed 
in the case of equipment and any supplies imported from overseas 
for they cost appreciably more than they do in the United States, 
because of import duties and transportation charges. These differ- 
ences in cost result in a change in emphasis in planning productions. 
In many cases the recording equipment is the controlling factor in 
scheduling, and production planning is centered around the avail- 
ability of the recorder. 

The Westrex Corporation serves only those studios located outside 
of this country. It is, therefore, essential that the equipment 
provided meet these conditions fully. To accomplish this, the West- 
ern Electric recording and re-recording equipment has been repack- 
aged to increase portability and versatility, while at the same time 
holding cost to a minimum. This matter of cost is particularly 
important in many countries because of governmental restrictions 
placed on dollar expenditures. Incidentally, it is interesting to note 
that the current price of this recording equipment is appreciably less 
than that of equivalent prewar equipment, despite the numerous 
improvements which have been made. 

There are four types of Westrex recording channels. The Series 
700 system is a de luxe studio channel which can be used for 35-mm, 
density or area, 100-mil standard or 200-mil push-pull recording, or 
for 16-mm, standard area or density tracks. This system is very 
similar to the Western Electric Series 400 film recording system which 
has been described in detail elsewhere. 1 A two-channel mixer is 
supplied with this system in a floor mounting cabinet. 

Fig. 2 shows the Series 600 system which is an all-purpose channel 
for recording 35-mm, 100-mil standard or push-pull track, density or 
area, or 16-mm standard density or area track. Essentially, it is 
the Series 700 system stripped of several of its operating features. 



1949 



RECORDING EQUIPMENT 



239 



The automatic control, the built-in punch, and slater have been 
eliminated. The recorder and its quality of results are unchanged 
but elimination of these operating features has reduced the cost, 
weight, and size. As an example of its portability, Praesens Studio, 
Zurich, Switzerland, has one installed in a lV4-ton Austin truck which 
has been used throughout Central Europe. Incidentally, any one or 
all of the features which have been eliminated can be added to the 
Series 600 system if and when required. 

The series 500 system is the smallest of the double-film recording 
systems. It records 35-mm or 16-mm standard track sound and is 







Fig. 2 Westrex Series 600 recording system. 



the same as the Western Electric Series 300 system previously de- 
scribed. 2 In both weight and bulk it is less than half the physical 
size of the Series 600 system and is therefore particularly suitable for 
usage requiring a high degree of mobility. 

The Series 200 system is a single-system, 35-mm, 100-mil standard 
track density channel which can be used with either Wall, Mitchell, 
or Akeley newsreel cameras. A detailed description of this system 
has been given previously by Hopper and Moody. 3 

In all these Westrex recording systems except the newsreel Series 
200 the change from 35-mm to 16-mm recording, or vice versa, is 
accomplished by means of a set of conversion parts. The change 



240 



WARN 



September 



can be made within half an hour by the normal operating personnel. 
The change from density to area, or vice versa, is also accomplished 
with a set of parts, in this case consisting chiefly of the modulator 
unit and light valve. Direct positive recording is also being made 
available by means of a conversion kit. 

There are two types of Westrex re-recorders. One is for 100-mil 
standard density or area track and the other for 100-mil standard, 
100-mil push-pull, and 200-mil push-pull tracks, density or area. 




Fig. 3 Westrex M4AB re-recording mixer console. 

On the push-pull re-recorder the change in tracks is achieved simply 
by turning an indicator knob and switching the phototube control 
from standard to push-pull. These re-recorders have a loop capacity 
of 25 feet. In addition, the base loop cabinet on which the re- 
recorder is mounted has a 30-foot capacity. There is a door at the 
top of the re-recorder for the extension of the loop upward and the 
base cabinet has removable side plates which make possible the use 
of adjacent cabinets for the running of very long loops. An auto- 
matic rewind with variable speed is available if required. 



1949 RECORDING EQUIPMENT 241 

Disk reproducers are available which provide 33 Vs- and 78- 
revolution-per-minute speed operation, both with a flutter content of 
less than 0.1 per cent. One motor is used for both speeds, the change 
in speed beng accomplished by reversing the direction of rotation 
of the motor and translating this reversal into a speed change by 
means of specially designed overriding clutches. Two types of re- 
producers are available. Either can be used for both vertical and 
lateral reproduction but one is slightly more suitable for vertical 
while the other favors lateral reproduction. 

The Westrex re-recording mixer consoles are made on the building- 
block plan in self-contained sections of four positions each. The 
first section includes the monitoring and intercommunication facil- 
ities. Additional sections may be added to increase the number of 
input channels as required. The unit shown in Fig. 3 is a two-section 
console with a capacity of eight input channels. 

More than 70 channels of these new equipments have already been 
installed in studios throughout the world. To achieve continuing 
good results it is essential that these studios keep up to date on prog- 
ress in recording techniques and equipment developments. To as- 
sist in achieving the desired results Westrex has built up an organiza- 
tion of trained recording personnel located in London, Paris, Bombay, 
Shanghai, and Buenos Aires. This service program has already 
shown worth-while results in maintaining recording standards, and 
should assist the foreign studios to keep abreast of developments in 
Hollywood and to bring worth-while developments from abroad to 
the attention of Hollywood, to the benefit of the industry as a whole. 

REFERENCES 

(1 ) F. L. Hopper and E. W. Templin, "New de luxe sound recording equipment 
and its system applications," presented October 27, 1948, at the SMPE Convention 
in Washington. 

(2) E. W. Templin, "New combination 34-mm and 16-mm portable sound re- 
cording system," J. Soc. Mot. Pict. Eng., vol. 53, pp. 159-183; August, 1949. 

(3) F. L. Hopper and R. C. Moody, "A simplified recording transmission sys- 
tem," /. Soc. Mot. Pict. Eng., vol. 47, pp. 132-142; August, 1946. 



The Picture Splice as a 
Problem of Video Recording* 

BY F. N. GILLETTE 

GENERAL PRECISION LABORATORY, PLEASANTVILLE, NEW YORK 

Summary Producing an invisible picture splice is one of the major prob- 
lems of present-day video recording. The various quantities which must be 
controlled to produce an invisible splice are enumerated with special empha- 
sis on the persistence characteristic of the cathode-ray-tube phosphor. 

INTRODUCTION 

THE TERM "video recording" might be defined as the process of 
making a photographic record of the picture portion of tele- 
vision-program material from the face of a cathode-ray tube. It 
involves a combination of the photographic and television arts. This 
union gives birth to a number of problems of technique which 
were not encountered in the practice of either of the parent arts. 

This paper will consider just one of these problems, that of making 
the picture splice invisible. Most of the many factors involved here 
will be covered as briefly as possible in order that more time can be 
given to a consideration of the cathode-ray-tube phosphor and its 
influence on the splice. 

To avoid certain ambiguities that would otherwise come up it is 
assumed at the outset that the film produced by video recording is 
to be used for theater projection and that it is produced by the direct- 
positive method. That is, that a positive film is obtained in a single 
photographic step by exposing the film to a negative video picture 
on the cathode-ray tube. 

Since the motion picture and television industries are both very 
large and are firmly standardized on their present frame rates of 
24 and 30 frames per second, video recording equipment is obliged 
to take 24-frame pictures of 30-frame events. The way in which this 
is accomplished is illustrated in Fig. 1. The upper figure represents 
the vertical scan of the television system. The scanning beam starts 
at the top of the picture, progresses at a constant rate to the bottom 
and returns rapidly to the top to start the next scan. A single sweep 

* Presented April 5, 1949, at the SMPE Convention in New York. 
242 SEPTEMBER, 1949 JOURNAL OF THE SMPE VOLUME 53 



SPLICING IN VIDEO RECORDING 



243 



down the picture is called a "field" and has a period, including the 
return time, of Vso of a second. 

The television system uses interlaced scanning in which only the 
alternate lines of the picture are scanned in one field, with the inter- 
vening lines scanned by the next field. Thus a television frame em- 
braces two fields and has a period of Vso of a second. 

The lower figure shows the timing diagram of a motion picture 
camera, modified to fit video recording requirements. The time 
ti indicates the start of an exposure, this exposure continuing to 
ti. A second exposure starts at U and continues to U. The interval 
beteen t 3 and U is l /u of a second as required by the motion picture 
system. The duration of each exposure is Vso of a second, allow- 
ing one full television frame to be recorded on each frame of film. 






\ \ 


\ 

\ 


\ \ 




\l 


\J \l 




5T V 


\1 








fa Ci, u CrtMtAT t* 





Fig. 1 Timing diagram. 

The exposure timing mechanism constitutes the major difference 
in various video recording equipments now in service. In some cases 
an electronic timing circuit blanks the cathode-ray tube thus provid- 
ing an electronic shutter. In others a mechanical shutter is used. 
Much of the following discussion will apply alike to both types of 
equipment. Where differences exist they will be pointed out. 

It is indicated in the figure that the interval available for film 
pulldown, t 2 to 3> is Vwo of a second, which is 72 degrees of the camera 
cycle. The shortness of this interval made necessary the design oi 
special cameras for video recording. At present there are several 
16-mm movements which meet this requirement and at least one 
35-mm movement. 

Projecting certain points from the camera diagram to intercept 
the television diagram shows that the beginning and the end of an 



244 GILLETTE September 

exposure coincide in vertical position on the cathode-ray tube, and 
that three television fields are involved in the exposure of each frame 
of film. Of the first and third of these fields only such segments are 
included as will add up to one field. The region on the film where 
these two picture segments join is called the ''picture splice" in this 
paper. 

The two exposures shown in the figure indicate that the picture 
splice will occur at two different positions. In following frames the 
splice will alternate between these two positions which differ in 
phase by one half of a television field. This is a significant point. 
It means that no matter how the camera is phased with respect to the 
television system at least one of the two splices will lie in the picture area. 

It is for this reason that the quality of the picture splice is of such 
concern. Since the splice cannot be hidden by means of phasing the 
only alternative is to make it invisible. This requires that there 
be no change in picture brightness or structure above, below, or 
coincident with the splice. The factors which oppose this result are 
the subject of the present paper. 

STRUCTURAL DEFECTS 

Changes in picture structure have been mentioned as a source of 
visible splice defects. Some elaboration of this point is in order. 
The scanning mechanism of television breaks the picture down into a 
number of discrete horizontal lines, a total of 525 per frame, with some 
500 of the lines in the useful picture area. Presenting these lines 
so that they are clearly resolved will add nothing to the clarity of 
the picture so that one normally would adjust the resolution of the 
photographic and projection equipment to conceal the line structure 
by merging each line with its neighbor. If overdone this action 
will lose detail in the picture so that one would attempt to hold the 
resolution of this part of the system somewhere between 400 and 
500 lines, using here the television method of counting lines. 

The success of this step depends upon the accuracy and stability 
with which each horizontal line is registered in its correct position on 
the film. If the lines of one field in a particular frame are displaced 
vertically with respect to the other field of that frame, the picture 
is no longer correctly interlaced, and if the displacement is an appre- 
ciable fraction of the space between lines, the lines become paired. 
In this case the picture contains but 250 lines, and with the system 
adjusted as suggested above, 250 lines will be resolved with ease. 



1949 SPLICING IN VIDEO RECORDING 245 

There are many sources of line displacement, some of which are not 
at all connected with the splice or the video recording equipment, but 
even these often serve to betray the location of the splice. If one 
recalls that a frame bearing a splice in the middle of the picture is 
assembled from three television fields, the reason for this effect may 
be seen. The bottom section of the picture is a combination of 
fields 1 and 2 while the top section is a combination of fields 2 and 3. 
A vertical displacement which occurs only in field 1 will produce 
visible line structure only in the bottom half of the picture leaving the 
top half smooth. The transition from structure to no structure is a 
very effective eyecatcher. 

An example of line displacement, which is characteristic of television 
in general and not specifically of video recording, is that which is 
caused by variation in the repetition frequency of the horizontal 
synchronizing pulses. The frequency is controlled at the transmitter 
by tracking the 60-cycle power-line voltage. Since the power line 
does not usually constitute a completely stable reference frequency, 
any frequency which is controlled by the power-line frequency will 
show a certain amount of random deviation. Such deviations are 
generally small, but the deviation required to produce a significant 
vertical displacement of the scanning lines is also small. Conse- 
quently, it is currently believed that frequency deviation of the 
horizontal pulses is a fundamental source of picture defect, which 
cannot be eliminated by any practical modification of the video 
recording equipment. 

.Other sources of structural defect are found in the video recording 
equipment. Of these several might be mentioned. Clearly any 
variation in picture size may make accurate superposition of two 
successive fields impossible. For this reason it is highly desirable 
to regulate all supply voltages which have any effect on deflection 
amplitude. This presents no difficulty except for the accelerating 
potential which is usually of the order of 30 kilovolts. Commercial 
regulators are available for this range, but they cannot cope with the 
type of current variation introduced by the gating action of elec- 
tronic-shutter equipment. Consequently it is common practice to 
shunt the output of the supply with a large capacitor, a practice which 
makes operating personnel very respectful toward this part of the 
equipment. 

Film motion may also create a structural defect. Since each line 
of the picture is registered on the film during a particular portion of 



246 GILLETTE September 

the exposure interval, film motion during any part of the exposure 
will serve to displace certain lines with respect to the remainder. 
Incorrect camera phasing may allow the exposure interval to extend 
into the pulldown interval resulting in gross displacement of lines at 
the splice. Line pairing over a considerable area of the picture may 
be caused by a minute amount of film creep. With some movements 
such creep might be introduced by the action of a register pin which 
is in motion during the exposure. In any case, very careful design 
is required to avoid any trace of film motion. 

BRIGHTNESS DEFECTS 

Brightness defects can also serve to make the splice evident. 
An abrupt brightness discontinuity will be observable simply by 
comparison of adjacent areas. A more gradual transition will be 
noticed primarily as flicker. The fact that the picture splice occurs 
in a given location only on alternate frames means that any brightness 
defect associated with the splice will give rise to 12-cycle flicker. In 
either case the brightness defect need not be large to be annoying 
to a critical observer. 

Screen brightness is, of course, related to the exposure received by 
the film, the exact relationship being determined by the intervening 
photographic processing. When the recording is a direct positive, 
the photographic step will have a gamma of about 2.5. This means 
that a small exposure difference will give rise to a screen-brightness 
difference which is two and a half times larger. Obviously very close 
control of the exposure is required. 

If the exposure interval determined by the camera is not exactly 
equal to the period of a television frame an exposure defect will be 
introduced. With electronic-shutter equipment the effect is con- 
centrated in the lines right at the splice, either as doubly exposed 
lines or as lines which receive no exposure. This would be a serious 
defect, but its prevention is not difficult. Since each television 
frame contains exactly 525 horizontal scanning lines it is possible to 
use pulse-counting circuits to insure that each exposure interval 
contains the correct number of lines. 

Incidentally, counting pulses to determine the exposure provides 
a system which is quite tolerant to variation in frame rate of either 
television or camera. In fact, the two systems need not operate at the 
same frame rate; a point of possible advantage if signals originating 
at a distant point are to be recorded. 



1949 SPLICING IN VIDEO RECORDING 247 

Mechanical-shutter equipment depends upon precise construction 
of the shutter and exact control of its rotation rate to achieve timing 
accuracy. Consequently, the camera must be locked in frequency 
to the television signal. Even with the two systems locked the 
inertia of the camera may prevent adequate accommodation to rapid 
change in television frame rate. To prevent such effects the two 
systems should be given the same time constant. 

The effect of a timing error in mechanical-shutter equipment will be 
considered in a later section. Here it is only noted that it differs from 
that outlined above for the electronic shutter. 

PHOSPHOR PERSISTENCE 

Another source of exposure error may be found in the phosphor of 
the cathode-ray tube. Since this factor has not received much public 
attention to date, it will be given closer scrutiny than has been given 
the preceding points. 

The films which are useful in video recording are all very slow films 
and are sensitive only in the blue region of the spectrum. Thus 
a satisfactory phosphor must have a considerable blue component in 
its light output. This fact plus certain features of operating con- 
venience seems to have led all workers in the field to select the type 
Pll phosphor as being the most acceptable. Consequently, the fol- 
lowing discussion will be confined exclusively to the Pll phosphor. 

The light emitted by an element of area of a phosphor is not 
restricted to the very short interval during which the electrons of the 
scanning beam impinge upon that area, but instead continues for an 
appreciable time thereafter. The rate at which the intensity of 
emission falls off after scanning is characteristic of the particular 
phosphor. For the Pll phosphor the decay is of the type shown in 
Fig. 2. 

The figure shows the instantaneous intensity of emission plotted 
as a function of time. According to the present standards of phosphor 
designation any Pll phosphor will follow this type of curve which is 
simply the reciprocal of some power of time. The exponent in the 
expression may have any value between 1 and 2. Experimental 
curves supplied by various manufacturers indicate exponents ranging 
from about 1.1 to about 1.4. Since a large exponent is desirable, at 
least for electronic-shutter equipment, a value of 1.5 has been used 
for this diagram, a value slightly higher than is justified by available 
data. 






248 GILLETTE September 

The amplitude factor has been adjusted to yield an intensity of 
10 per cent of the initial intensity at 500 microseconds, a value which 
fits the data of several manufacturers. Clearly the simple inverse 
power law cannot apply in the neighborhood of zero time since infinite 
values of intensity would result. For this region, extending out to 
250 microseconds, linear decay has been assumed. 

The total light output of any element of the phosphor is proportional 
to the integral of this curve, that is, to the area under the curve. 
That portion of the total light which is effective in exposing the 
corresponding element of the film is determined by carrying out the 




Fig. 2 Decay characteristic of Pll phosphor. 

integration for just that interval of time, different for each line of the 
scan, during which light from the phosphor is permitted to reach the film. 

The effective exposure of the element of film is assumed to be 
proportional to this integral. That assumption is not really justi- 
fied in view of the well-known failure of the reciprocity law when ap- 
plied to exposures of such short duration. However, no information 
is available on which to base a more accurate statement. 

The mechanism that prevents light from reaching the film, thus 
limiting the period of integration, is obviously the closing of the 
shutter if the equipment contains a mechanical shutter. If the 
shutter is electronic there is actually no interruption of the passage 
of light from phosphor to film. Here the limiting action is the motion 
of the film during its transport period. While the film is in motion 



1949 



SPLICING IN VIDEO RECORDING 



249 



incident light does not contribute to the formation of a particular 
image point, but instead is spread over a large area of the film, thus 
contributing nothing but a general fog. 

PERSISTENCE IN RELATION TO THE ELECTRONIC SHUTTER 
In this respect electronic and mechanical shutters behave quite 
differently and require individual consideration. The case of the 
electronic shutter, illustrated in Fig. 3 will be considered first. 

The top figure simply repeats the camera cycle which is shown in 
Fig. 1. The pulldown interval shown here is the maximum available 
for pulldown and is greater than the time actually required by the 
camera. 



r 



J 



f/esr 
Line. 




Fig. 3 Timing diagram electronic shutter. 



The central figure shows the actual pulldown interval of the 
camera. It will be noted that the end of actual pulldown has been 
made to coincide with the end of the available interval, this phasing 
being the most advantageous, as will be seen. 

The bottom figure shows the light-output curves of the first and 
last of the 525 lines of the television frame. The 523 intervening 
lines are not shown because of the crowding that would result. The 
lines just outside the exposure interval are not shown because they 
do not exist on the cathode-ray tube, being blanked out electronically 
by the timing circuits. 

The exposure for each line is calculated by integrating from the 
time of occurrence of that line to the time at which pulldown starts, 
indicated by the dotted line. The first line of the frame is thus inte- 
grated over a very long time and the exposure is essentially equal to 



250 



GILLETTE 



September 



the total light output from that line. The last line is integrated over 
a relatively short time, indicated as At, and if the persistence is long 
with respect to At a reduced exposure will result. At is equal to 
the difference between the time available for pulldown and the time 
actually used for pulldown and its value depends upon the particular 
intermittent used in the camera. Generally it will be something 
between 1 and 2.5 milliseconds. 

The exposure integration has been carried out for a sufficient 
number of different intervals to establish the curve shown in Fig. 4. 
From this curve it is possible to determine the relative exposure 




25 10 V to ? Z 

Fig. 4 Relative exposure versus line placement. 

value for any line in the frame once the characteristics of the inter- 
mittent are known. 

The curve is a plot of relative exposure against time of occurrence 
of the scanning line. The time scale is reversed, increasing to the 
left, and indicates the time by which each line precedes the beginning 
of pulldown. As an example of the use of the curve, the position of 
the last scanning line is indicated at t equals At. The value of the 
ordinate at this point is the relative exposure of the last scanning 
line. Each preceding line would be placed 63.5 microseconds farther 
to the left, this being the period of the horizontal lines. The position 
of the first scanning line is indicated at the extreme left. 

Information extracted from this curve is shown in another form 
in Fig. 5. For this figure At is assumed to be 2 milliseconds. The 






1949 



SPLICING IN VIDEO RECORDING 



251 



vertical bars represent the horizontal scanning lines in the vicinity 
of the splice, the height of each bar indicating the relative exposure 
contributed by the line. The vertical scale is expanded to emphasize 
the differences that exist. The horizontal co-ordinate indicates 
the location of the line in the vertical dimension of the picture. It 
too is expanded so that individual lines may be shown. 

The effective exposure for an extended area will be an average of 
the individual line exposures, this average being shown in the dia- 
gram by the two horizontal lines. They indicate the average ex- 
posure on the two sides of the picture splice to differ by some 6 per 



fOO% 
























n 




n 




n 




n 




n 




n 
















































9? 














































90 














































8f\ 









n 




n 




n 




n 



























LINE POSITION 

Fig. 5 Relative line exposure in picture-splice area. 

cent. Multiplying this difference by the photographic gamma in- 
dicates a brightness difference at the projection screen of 15 per cent, 
a value which will certainly be visible. 

The defect thus calculated is so large that one would tend to doubt 
the validity of the procedure except for the fact that Pll tubes have 
been encountered which do exhibit a persistence defect of this magni- 
tude. Other Pll tubes seem to be completely satisfactory. 

A similar calculation has been carried out, starting with an assumed 
screen-brightness difference which is acceptable and then working 
backward to determine a corresponding phosphor decay curve. For 
this curve the exponent in the inverse power law has a value which is 
very close to 2. The existence of satisfactory Pll tubes may mean 
that some tubes actually follow an inverse square law, although sub- 
stantiating data have not been found. It may alternatively mean 



252 



GILLETTE 



September 



that the inverse power law is not a satisfactory approximation to the 
facts, particularly in the tail of the curve where the intensity values 
are very low and have not been checked experimentally. 

PERSISTENCE IN RELATION TO THE MECHANICAL SHUTTER 

In considering the action of a mechanical shutter, the situation 
will be found to be quite different. Electronic blanking is not used 
and all of the lines of the television scan are shown on the cathode-ray 
tube. Thus lines which have actually been scanned on the tube prior 
to the beginning of the exposure interval may contribute significantly 
to the exposure of the film by virtue of the phosphor's persistence. 




o >oo 

MICROSECONDS 



zoo 300 400 foo 

Fig. 6 Mechanical-shutter action. 



The mechanical shutter is designed so that its closing edge crosses 
any point in the shutter plane exactly Vso of a second after that same 
point was crossed by the opening edge. For a particular line which is 
scanned just before the shutter opens, the first part of its light output 
is blocked by the shutter, and only a segment of the tail of the output 
curve contributes to the exposure of the corresponding element of 
the film. However, since each line is scanned repeatedly at intervals 
of Vso of a second, the same line is scanned again just before the 
shutter closes, and this time the initial portion of the light output 
reaches the film and only a segment of the tail of the curve is blocked 
by the shutter. If everything is working to perfection, the con- 
tributions from the two scannings of the line add up to give a total 



1949 



SPLICING IN VIDEO RECORDING 



253 



exposure exactly equal to that obtained from a single scanning of the 
line without the interruption of the shutter. 

Thus it seems there is no first-order effect of persistence with me- 
chanical-shutter equipment, so that it should be possible to use any 
Pll tube, or even phosphors of longer persistence. 

However, there is a second-order effect which should be considered. 
If either the interval between scannings of a line or the open interval 
of the shutter should be incorrect, then the two scannings of the line 
would not be symmetrically located with respect to the opening and 
closing actions of the shutter and the sum of the two contributions 




7OQ 



Fig. 7 Effective light output correct timing. 

would not equal the desired total. Calculating the exposure error 
that would result from a given error in timing will provide an evalua- 
tion of the tolerance of the system to timing errors. 

The steps which are involved in such a calculation can be explained 
in connection with Fig. 6. The upper figure is again the persistence 
curve of the Pll phosphor. The lower curve shows what is thought to 
be the shutter action of the Eastman television recording camera. 
The conditions to which these curves apply involve a 2-inch lens, an 
aperture of //2.6, and an object distance of 30 inches. The vertical 
co-ordinate for the shutter curves represents the relative transmission 
of the effective aperture of the system at any instant. The time scale 
is the same as that for the light-output curve. 

To determine the relative exposure for each of the two scannings 
of a line located as shown with respect to the shutter cycle, each value 



254 



GILLETTE 



September 



of the light-output curve must be multiplied by the corresponding 
transmission values of the two shutter curves. This step is illustrated 
in Fig. 7. 

Here curve 1 shows the effective light output for the first of the 
two scannings of the line. Curve 2 shows the same quantity for the 
second scanning. Curve 3 is the sum of curves 1 and 2 and represents 
the total light which is effective in exposing the corresponding area 
of the film. As expected, curve 3 is identical with the original light- 
output curve of the phosphor. 

Fig. 8 shows the same group of curves, but they represent erroneous 
timing in that the closing of the shutter has been retarded 100 micro- 
seconds with respect to the second scanning of the line. This pro- 



1.0 




4OO 



too 



Fig. 8 Effective light output retarded closing. 

duces a defect in the total output curve which has been emphasized 
by showing with a dashed line the desired shape. The resulting 
exposure error is proportional to the area between curve 3 and the 
dashed line. 

The same calculation was carried out for several values of shutter 
error and the various exposure errors were determined. The results 
are shown in Fig. 9. Here the horizontal co-ordinate is the shutter 
error in microseconds and the vertical is the exposure error which 
results. If again one -averages the exposure over a small area and 
multiplies by the photographic gamma it is seen that a timing error 
of around 30 microseconds will produce a screen-brightness defect 
of about 6 per cent. Since this defect would be quite visible it 
follows that timing which is accurate to 0.1 per cent is not good enough. 



1949 



SPLICING IN VIDEO RECORDING 



255 



It should be pointed out that this result applies only to lines which 
are scanned almost in coincidence with the opening and closing of the 
shutter, in other words, to some 6 to 12 lines at the splice. The effect 
diminishes rapidly for lines outside this group. 

By selecting a phosphor with a faster decay, the area may be 
narrowed slightly but the magnitude of the error will be increased. 
Conversely, a slower decay curve will result in a smaller brightness 
error, but will spread it over a larger area. 



RETARDED 



Fig. 9 Exposure error versus shutter error. 



CONCLUSION 

The comparatively detailed consideration of phosphor persistence 
is intended simply as an example of the type of quantitative study 
that must be given each of the many factors which affect the quality 
of the recorded picture. The goal in each case is to reduce the mag- 
nitude of any defect to a level below the threshold of detectability 
for that defect. At present the threshold values are largely estab- 
lished by the transmitted television picture which often contains 
defects of greater magnitude than those contributed by the recording 
process. As the transmitted picture is improved the threshold values 
will have more fundamental origins, usually some characteristic of the 
human eye. These latter values are the ones by which the equipment 
designer must be guided if the resulting equipment is to achieve 
acceptance for any extended period. 



Navy Electronic Shutter Analyzer 

BY W. R. ERASER 

U. S. NAVAL PHOTOGRAPHIC CENTER, ANACOSTIA 20, D. C. 



Summary A new electronic shutter analyzer employing a two-gun 
cathode-ray oscilloscope with two phototubes has been developed by the 
Navy. This device is designed to permit the rapid analysis and solution of 
numerous problems commonly encountered in photography including: (1) 
shutter operation and efficiency; (2) shutter-flash synchronization; (3) 
shutter-solenoid delay; (4) flash-gun-switch, solenoid-shutter delay; (5) 
internal-shutter-switch contact time; (6) switch or electrical contact ef- 
ficiency; (7) diaphragm calibration; (8) duration and intensity of light as 
emitted by flashbulbs and some gaseous discharge tubes. 

INTRODUCTION 

THE FUNDAMENTAL PROBLEM in everyday photography is to make 
sure that the correct amount of light is permitted to strike the 
unexposed negative in the camera. Since a film of infinite latitude 
has not as yet made its appearance, and narrow latitude color film has, 
it becomes increasingly necessary to measure accurately the effective 
exposure time. 

The importance of "getting that picture," whether it be during a 
battle or in a research laboratory, warranted development of a testing 
device that would rapidly and graphically furnish the information 
necessary to calibrate the cameras properly. The problem was to 
develop an equipment which could be operated by a naval pho- 
tographer and which would be useful in the solution of a majority of the 
photographic problems. The Research and Development Department 
of the United States Naval Photographic Center, under the general 
supervision of the Bureau of Aeronautics, conducted a survey of 
camera-shutter testing problems as encountered at various Naval re- 
search laboratories, test stations, and the like. 

On the basis of this survey, it was decided to utilize the visual type 
of presentation on a cathode-ray oscilloscope as outlined in the 
American War Standard Specification Z52. 63-1946. However, 
Specification Z52. 63-1946 covering a "Method of Determining Per- 
formance Characteristics of Between-the-Lens Shutters used in Still- 
Picture Cameras" did not permit analysis of shutter-flash sjTichronism 

* Presented April 8, 1949, at the SMPE Convention in New York. 
256 SEPTEMBER, 1949 JOURNAL OF THE SMPE VOLUME 53 



SHUTTER ANALYZER 257 

or solenoid-shutter delays. It was considered that this limitation 
would be overcome by the simultaneous presentation of two curves on 
a cathode-ray oscilloscope which would represent two separate and 
distinct phenomena. Specifications were drawn up and a contract 
awarded the Triumph Manufacturing Company, Chicago, Illinois, for 
the development and construction of the Model 950 electronic 
shutter tester. Seyen months later the equipment was delivered to 
the Navy for acceptance tests which disclosed that the manufacturer 
had exceeded the requirements of the specification. The credit for the 
design and construction of the shutter tester, or more appropriately, 
shutter analyzer, must be given to E. J. Doyle and William Sturm, 
chief engineer and assistant engineer, respectively, of the Triumph 
Manufacturing Company. 

Before going into a more detailed description of the shutter an- 
alyzer, it is recognized that shutter-testing devices utilizing a cathode- 
ray oscilloscope and a phototube have been assembled and used in 
various laboratories. To the best of the author's knowledge, these 
early pioneer units have been assembled from odds and ends of labora- 
tory electronic equipment while, on the other hand, the Triumph 
Model 950 tester is completely engineered and is in production (see 
Fig. 1). 

DESCRIPTION 

A DuMont type 5SP7 5-inch dual-gun, long-persistence, cathode- 
ray oscillograph with a dual set of controls is the main component of 
the electronic shutter tester. Two GL-929 photoelectric tubes with 
associated cables and a rectified 120-volt direct-current source of 
illumination comprise the balance of the equipment (see Fig. 1). 

The shutter-tester, dual-gun, cathode-ray oscillograph has a dual 
set of conventional controls including horizontal and vertical beam 
positioning, focus, intensity, and vertical amplitude (Fig. 1). The 
horizontal amplitude of both curves, however, is simultaneously 
varied by a single control and may be linearly expanded approxi- 
mately 500 per cent. Sweep speeds of 1 millisecond, 10 milliseconds, 
and 100 milliseconds corresponding to frequencies of 1000, 100 ; and 
10 cycles per second are available by means of a selector switch. Both 
single sweep and repetitive sweep are furnished. Using the single- 
sweep position, each beam receives an intensifying pulse and the re- 
sulting curve will start at the left and then travel to the right. When 
using repetitive sweep, however, the resulting curve will never occur 



258 FKASER September 

at the same location on the tube. The only exception to this rule 
occurs when the frequency of the phenomenon under study is either 
equal to or is an even multiple of the sweep speed of the tube. In this 
case, the resulting curve or curves will appear to be stationary. Trig- 
gering of the sweep may be initiated by : 

(a) Information furnished to Channel I resulting from light 
energy as picked up by phototube 1. 




Fig. 1 Electronic shutter analyzer (tester) including the light box and two 

phototubes. 

(b) Information furnished to Channel II resulting from either 
light energy as picked up by phototube 2 or by the closure of an ex- 
ternal electrical circuit through the receptacle located on the top 
surface of tube 2. 

(c) Pressing the " trigger" button. 

(d) A momentary contact across the " trigger external" termi- 
nals. 

A timing oscillator furnishes alternate blanking and intensifying 
pulses of either 1-millisecond or Vio-millisecond duration. These 



1949 



SHUTTER ANALYZER 



259 



timing pulses are superimposed upon both curves and provide a visual 
picture of the time relationship involved. 

An off-on toggle switch, a red indicator lamp, a fuse, and a ground- 
ing terminal complete the list of controls as found on the front panel 
of the shutter tester proper. The simplified functional block diagram 
of the tester is given in Fig. 2. 

OPERATION 

The electronic shutter tester, or more appropriately, the electronic 
shutter analyzer, is ideally suited for testing between-the-lens shut- 

S5P7 DUAL GUN C RO 







BLOCK DtAGffAM Of 
TRIUMPH MODEL 95O 

SHUTTIR AHAl YZCft 



f . ho it ml 2. Press Ext 

Fig. 2 Simplified block diagram of the shutter analyzer. 

ters. However, a considerable amount of information concerning 
focal-plane shutters and rot at ing shut ters, such as used in conventional 
motion picture cameras, may be determined through proper use of the 
tester. 

A between-the-lens shutter may be tested conveniently when 
placed between a source of direct-current illumination and either of the 
two phototubes. When the shutter with its lens is mounted on a 
camera with a removable or open back, the open back of the camera is 
placed as close to the light source as possible. The phototube, how- 
ever, must not be placed too close to the shutter as, in the case'of 
large-diameter (4-inch) aerial camera shutters, the angle of acceptance 



260 



FRASER 



September 







Fig. 3 Curve produced by a between- the- lens shutter operated at 
Vioo second with 1-millisecond timing markers. 

of the phototube may be exceeded. For a given set of conditions, 
moving the phototube away from the lens or moving the light source 
away from the back of the camera will decrease the vertical amplitude 
of the curve on the oscilloscope as produced by the light passing 
through the shutter. The height of this curve may also be varied by 
the appropriate "vertical-amplitude" control of the analyzer. Fig. 3 
illustrates the type of curve produced by a well-known shutter when 
set at Vioo of a second with a maximum diaphragm opening of //4.7. 
The second gun of the cathode-ray oscilloscope in this case furnishes 
a convenient baseline. It can be seen that a negligible portion of the 




Fig. 4 The small curve was produced by wiping action of internal 
shutter contacts at the 5-millisecond delay setting. The large curve 
was produced by a Vioo-second shutter. 



1949 



SHUTTER ANALYZER 



261 




Fig. 5 Curves produced by the shutter of Fig. 5 but with a 20- 
millisecond delay setting. 



curve at the extreme left has been lost because of the delay required 
for triggering the sweep. Even this small loss could have been elim- 
inated by using an external method of triggering or by repetitive 
sweep if it had been desirable to analyze closely the opening portion 
of the shutter cycle. As a 1-milliseccnd timing pulse was used, each 
dot plus a blanking period is equal to 0.001 second. If a Vio-milli- 
second (0.0001-second) timing pulse had been used, the number of 
dots on the curve would have been increased by a factor of ten. 

Fig. 4 illustrates the time relationship when the same shutter as 
above is manually actuated to check operation of the internal shutter 




Fig. 6 Curve produced by the shutter of Fig. 3 with the baseline 
moved halfway up the curve, 



262 FRASER September 

contacts at the 5-millisecond delay setting. By counting the 1- 
millisecond timing dots, it is found by inspecting the small curve that 
the shutter contacts are making a good contact for approximately 5 
milliseconds and that the shutter was wide open approximately 5 
milliseconds after the initial closure of the shutter contacts. A 5- 
millisecond delay flashbulb, when used on this camera, would there- 
fore, not be in perfect synchronism with the shutter and it would not 
be necessary to waste a flashbulb to verify this condition. Fig. 5 
illustrates the time relationship at the 20-millisecond delay setting 
and it can be seen that a 20-millisecond delay flashbulb would be in 
synchronism with the shutter. 




Fig. 7 -Curve produced by the shutter of a 24-inch focal-length K-18 
aerial camera at the maximum aperture of //6. 

It is well known that the effective exposure produced by a between- 
the-lens shutter can be determined by noting the length of time during 
which the shutter is passing more than 50 per cent of the maximum 
amplitude of light intensity as indicated on a curve of light trans- 
mission versus time. Referring to the curve of Fig. 3 as produced by a 
shutter set at Vioo second and drawing an imaginary line parallel to the 
baseline and midway between the baseline and peak amplitude, it will 
be noted that the portion of the curve thus cut off by this imaginary 
line has 7-millisecond timing markers. The effective exposure time is 
therefore 7 / 10 oo or 1 / 140 second. Fig. 6 illustrates how the baseline may 
be moved halfway up the curve and then the number of timing marks 
may easily be counted to determine the effective exposure. The total 
"open time" or "action-stopping time" of the shutter is determined by 



1949 SHUTTER ANALYZER 263 

counting all the timing markers on the curve of Fig. 3. The shutter 
efficiency is equal to the ratio of : 

effective exposure time 7 milliseconds 

, . i r- - = -n -IT :r = 64 per cent. 

total open time 11 milliseconds 

Fig. 7 was obtained by the action of the shutter of a K-18, 24-inch 
focal-length aerial camera with a maximum aperture diameter of 4 
inches. It is quite apparent that a definite "shutter bounce" has 
occurred as the shutter reached its maximum aperture. This portion 
of the curve may be more closely analyzed by either expanding the 
curve horizontally or by switching from the 100-millisecond sweep to 
the 10-millisecond sweep. 

FOCAL-PLANE SHUTTERS 

Focal-plane shutters with constant slit widths present a more 
difficult problem of analysis than do between-the-lens shutters. Be- 
tween-the-lens shutters whether wide open or barely open, are passing 
light which simultaneously strikes the entire area of the film during 
the "total time open" cycle of the shutter. Focal-plane shutters with 
constant- width slits scan the negative and the exposure depends upon 
slit width and slit velocity. The efficiency, however, is a constant 
depending upon the physical construction of the camera and the 
/ stop and is given by the formula 

efficiency = E = W -s- (w + j\ , 

where 

W = slit width 

D = distance between focal plane and curtain 

/ = stop of lens. 

A curve on the cathode-ray oscilloscope resulting from the travel of 
the focal-plane shutter slit closely resembles the curve produced by 
the between-the-lens shutter of Fig. 3. If the slope of the opening 
part of the curve is the same as the slope of the closing part of the 
curve, it is reasonable to assume that the curtain velocity at the be- 
ginning of the exposure is equal to the curtain velocity at the end of 
the exposure. The curtain velocity or exposure during the "flat" 
portion of the curve, however, is not so easily determined. As the 
effective exposure time is that required for the slit to move a distance 
equal to the width of the slit itself, the effective exposure time for any 
point may be determined by appropriately masking off the ground 



264 FRASER September 

glass as located at the focal plane. For example, when the curtain slit 
is Y 4 inch wide, a parallel V4-mch-wide s lit on the ground glass would be 
left unmasked. The location of this slit could, for example, be placed 
at the geometric center of the ground glass. Fig. 8 shows a curve with 
0.0001-second timing marks obtained by this test method utilizing 
collimated light. The time required to pass from zero to maximum 
amplitude may be designated as h, and fe, the time to pass from maxi- 
mum amplitude to zero. The slit velocity during the short time re- 
quired for the slit to travel a distance equal to its own width may be 
assumed to be practically constant and then t\ = t?. In this case, ti is 




Fig. 8 Curve produced by a focal-plane shutter that has moved 
a distance equal to the shutter slit width. (0.0001-second timing 
markers.) 

the time required for the slit to travel a distance equal to its own 
width. Then, 

c 

velocity of slit V s = - 
h 

where S = slit width. Effective exposure time T e = S/V S . 
Substituting, 



From Fig. 8, it can be determined that the effective exposure time 
at the center of the 4- X 5-inch plate is approximately equal to 
0.0012 second or Vsso second. A series of these slits may be placed on 
the ground glass and a corresponding number of similar curves will be 



1949 SHUTTER ANALYZER 265 

produced. For example, a slit could be placed at the top, center, and 
>ttom of the giound glass and the effective exposure corresponding 
the three slit locations could be determined. Knowing the slit 
ddths, slit spacings, and the time intervals, the curtain velocity may 
computed at each of the three locations. 

PHOTOGRAPHIC FLASHBULB AND FLASHTUBE ANALYSIS 

The light emitted by flashbulbs may not only be analyzed from the 
idpoint of synchronization with the camera shutter but may be 
studied with respect to comparative intensity, duration of flash, and 
general shape of the light-output-versus-time curve. The shape of this 
curve may resemble that of Fig. 8 for 5- or 20-millisecond delay flash- 
bulbs or the curve may be flat on top for a long-duration flash as re- 
quired for use with focal-plane shutters. 

The analyzer may be used for studying the light-emission curves 
resulting from the discharge of capacitors through gas-filled tubes as 
developed by H. E. Edgerton of the Massachusetts Institute of 
Technology. Fig. 9 illustrates the characteristic type of curve pro- 
duced by most electronic flash equipment. Fig. 10 is a photograph of 
the curve produced from the light emitted by a well-known portable 
flash unit. Timing marks of 0.0001 second reveal that approximately 
3 /io,ooo second was required for the light to reach peak intensity while 
approximately 16 /io,ooo second had elapsed during the flash-decay 
period. The shape of this curve is typical for all electronic flashtubes 
including the strobotac, strobolux, and microflash. 

The sweep circuits of the analyzer were checked with signals fur- 
nished by a signal generator that had first been calibrated with the 
Bureau of Standards broadcast audio-frequency signals. The per- 
centage of error at frequencies up to 40 kilocycles was found to be less 
than */ 2 of 1 per cent. 

The accuracy of the tester sweep circuits was profitably utilized in 
the analysis of focal-plane-shutter slit speeds and deformations of slit 
shapes at high linear velocities. A strobotac was first calibrated by 
means of the shutter analyzer at a speed of 6000 revolutions per 
minute (100 cycles per second). With the analyzer sweep set at 10 
milliseconds or 100 cycles per second, the strobotac control was 
rotated until one stationary curve similar to Fig. 9 appeared on the 
screen. A strobolux, which has a much higher light output, was 
operated from the strobotac with phototube 2 placed in front of the 
strobolux while phototube 1 was in front of the strobotac. As the 



266 



FEASER 



September 




Fig. 9 Typical curve produced by an electronic flashlight source. 

strobolux frequency is controlled by the strobotac, two stationary 
synchronous curves appeared on the screen which indicated that the 
calibrated frequency of the strobotac had remained undisturbed. In- 
creasing the strobotac frequency until two pairs of curves appeared 
on the screen produced a calibrated 200-cycle-per-second pulse. The 
camera was loaded with film and the focal-plane shutter operated 
with the camera facing the strobolux. 

The images recorded on the developed negative were in the form of 
horizontal bars which are proportional to the shape of the shutter slit. 
The distance between bars depends upon the curtain velocity and the 
strobolux frequency which during the test was L /ioo and 1 / 2 oo second. 




Fig. 10 Curve produced by a portable speed lamp with 0.0001- 
second timing markers. 



1949 SHUTTER ANALYZER 267 

Leica-type and other cameras that are not equipped with removable 
backs present a more difficult problem since the reflected light must be 
utilized. A strip of aluminum foil was placed in the focal plane of a 
Leica camera and a No. 2 floodlamp operated from a 110-volt direct- 
current supply was used as the light source. Operation of the small 
focal-plane shutter exposed the aluminum foil to the light which, when 
reflected, triggered the sweep through the No. 1 phototube and pro- 
duced a curve that indicated the time required for the slit to traverse 
the film gate. 

MOTION PICTURE SHUTTER TESTING 

The rotating shutter of the conventional motion picture camera 
may also be analyzed to a certain extent by the shutter tester. A 
limited number of tests have been made using a 35-mm Mitchell 
motion picture camera operated at speeds varying from 10 to 100 
frames per second. Using repetitive sweep, numerous interesting 
curves were obtained by directing a 110-volt, direct-current spot- 
light through the aperture and picking up the light beam from an 
appropriately placed mirror. The camera tachometer frame-per- 
second dial readings were easily checked and the effect of varying the 
shutter angle from zero to 170 degrees was noted. The curve pro- 
duced at 170 degrees open-shutter angle had a flat top with symmet- 
rically sloping sides and closely resembled the curves produced by 
between-the-lens (Fig. 3) and focal-plane shutters. 

CONCLUSION 

In conclusion, it may be stated that an instrument capable of fur- 
nishing the answer to such a wide variety of photographic problems 
will be a welcome addition not only to the Services, but to the photo- 
graphic industry as well. 



Simultaneous Determination 
of Elon and Hydroquinone 
in Photographic Developers* 

BY HERBERT L. REES AND DON H. ANDERSON 

COLOR CONTROL DEPARTMENT, EASTMAN KODAK COMPANY, 
ROCHESTER, NEW YORK 

Summary A sample of the developer solution is diluted with a pH 5 
acetate buffer and its absorbancyf measured at two wavelengths in the 
ultraviolet region. The concentration of ElonJ and hydroquinone in a fresh 
unused developer solution can be determined directly from these two ab- 
sorbancies. Used or old developer solutions are analyzed by extracting the 
unoxidized Elon and hydroquinone with ethyl acetate. Absorbancy meas- 
urements made on the system before and after extraction serve to deter- 
mine the amount of Elon and hydroquinone present. 

INTRODUCTION 

THE PRESENT METHODS that have been available for determining 
the concentrations of Elon and hydroquinone in a developer solu- 
tion have necessitated a preliminary extraction in order to remove the 
Elon and hydroquinone from interfering materials. Lehmann and 
Tausch 1 have published an analytical method for Elon in which the 
Elon was extracted for several hours in a continuous extractor and 
then determined by an iodometric titration. Evans and Hanson 2 de- 
veloped colorimetric methods for both Elon and hydroquinone. The 
developer solution was extracted with ethyl acetate at a pR of approx- 
imately 8 and the Elon which was extracted in the ethyl acetate 
layer allowed to react with furyl acrolein. The color produced was 
measured on a filter photometer. The hydroquinone was determined 
by extracting it with ethyl acetate at about pH 3, adding potassium 
ferricyanide and sodium sulfite and measuring the color. 

In the method recommended by Baumbach 3 and Atkinson and 
Shaner, 4 hydroquinone was separated from the Elon by extraction at 

* Presented April 8, 1949, at the SMPE Convention in New York. 

t Where the transmittance of a solution is measured relative to the solvent, the 

National Bureau of Standards has recommended use of the term transmittancy 

with symbol T s and the term absorbancy, A s , where A s = logm T s . 

t Elon is the trademark of the Eastman Kodak Company for a photographic 

developing agent that is mono-methyl-p-aminophenol sulfate. 

268 SEPTEMBER. 1949 JOURNAL OF THE SMPE VOLUME 53 



PHOTOGRAPHIC DEVELOPERS 269 

pR 2 and was then titrated with iodine. By extraction of a separate 
sample at a pH of about 8, both Elon and hydroquinone were ex- 
tracted and titrated with iodine. The Elon concentration was then 
determined by difference. 

Evans, Hanson, and Glasoe 5 extracted hydroquinone at pH. 2, then 
adjusted the pH. to about 8 and extracted the Elon. Each extract 
was analyzed by means of a polar ograph. Similar extractions were 
also employed by Stott who then determined the concentrations of 
Elon and hydroquinone in the separate ethyl acetate layers by titrat- 
ing each potentiometrically with an acid solution of cerate such as 
eerie sulfate. 6 

Baumbach 7 extracted the developer solution at pH 8.0 to 8.5 with 
methyl acetate and Shaner and Sparks 8 used methyl ethyl ketone. 
The Elon in the solvent layer was titrated with hydrochloric acid and 
the hydroquinone plus Elon was then titrated with iodine. This 
method is subjected to large errors in the Elon analyses when less than 
one gram per liter of Elon is present. 

Levenson 9 in an evaluation of the various methods states that the 
potentiometric method of Stott is prone to give large errors, especially 
for Elon. He 10 has developed a modification in which he states the 
errors are reduced to 1 per cent for hydroquinone and 2 per cent for 
Elon. 

Although many of the existing methods give results of the required 
accuracy, the analyses are lengthy and considerable experience is re- 
quired on the part of the analyst for maximum accuracy. 

EXPERIMENTAL 

Studies of the ultraviolet absorption of Elon and hydroquinone 
showed that each had characteristic absorption peaks in the ultraviolet 
region. The rather large absorbancies necessitated dilution of the de- 
veloper solutions to secure a lower absorbancy which would be in the 
useful range of the Beckman Spectrophotometer. It was determined 
that a sufficiently stable solution could be obtained by diluting 1 milli- 
liter of developer sample with* 100 milliliters of pH 5 acetate buffer. 
The dilution should, of course, be changed to secure maximum accuracy 
if the concentrations of Elon and/or hydroquinone are very large or very 
small. The absorbancies of the mix ingredients other than Elon and 

* In order to speed the determination, 1.00 milliliter of sample was diluted with 
100 milliliters of acetate buffer. The buffer was measured with an automatic 
pipet. 



270 REES AND ANDERSON September 

hydroquinone were small enough to be considered constant and com- 
pensated for in the determination of Elon and hydroquinone. The 
magnitude of the basic mix (i.e., a mix containing all other constitu- 
ents except Elon and hydroquinone) absorbancies was small enough so 
that a change of 50 per cent in the concentration of any of the basic 
mix ingredients did not significantly change the absorbancy. This is 
illustrated by the developer used in this work which contributed a 
blank absorbancy of 0.010 at 270 millimicrons and 0.008 at 290 milli- 
microns. 

The method has been applied successfully to all developers contain- 
ing Elon and hydroquinone so far examined . 

The Elon and hydroquinone were Eastman Kodak chemicals and 
the inorganic chemicals were of photographic quality. 

The developer used in this work had the following composition: 



Constituent 


Concentration, 
Grams per Liter 


Sodium sulfite 
Elon 
Hydroquinone 
Sodium carbonate monohydrate 
Potassium bromide 


45.0 
(Refer to text) 
(Refer to text) 
50.0 
2.0 



The chemicals were dissolved in the order given. Slight warming 
was occasionally applied to get the Elon into solution. It was impor- 
tant that the Elon was in solution before the hydroquinone was added 
to minimize the oxidation of the latter. 

Typical absorption curves for Elon, hydroquinone, and the com- 
plete developer mix are shown in Fig. 1. From examination of the 
curves, it will be seen that at 290 millimicrons, where the maximum 
absorption of hydroquinone appears, there is also some absorption by 
the Elon. However, by measuring the absorption at 270 millimicrons 
in addition to the measurement at 290 millimicrons, it was possible 
simultaneously to determine the amount of Elon and hydroquinone 
present in a developer. 

ANALYSIS OF FRESH DEVELOPERS 

Reagents 

pH. 5 acetate buffer. Add 23 grams of anhydrous sodium acetate to 
58 milliliters of 2 molar acetic acid and dilute to 1 liter with distilled 



1949 



PHOTOGRAPHIC DEVELOPERS 



271 



water. Adjust the final pR of the solution to 5.00 =*= 0.02 with glacial 
acetic acid or sodium hydroxide. 

Cleaning solution. Mix one volume of denatured alcohol and one 
volume of 3 normal hydrochloric acid. 

Apparatus 

Beckman Spectrophotometer, Model DU, with ultraviolet accesso- 
ries. 

Fused silica absorption cells, 1 
centimeter. 






Procedure 

Dilute 1.00 milliliter of sample 
with 100 milliliters of pH. 5 acetate 
buffer. Determine the absorbancy 
of this solution at 270 and 290 
millimicrons. 

NOTE: Distilled water was 

used in the blank cell as a ref- 
erence liquid. Care must be 

taken to see that the distilled 

water and the acetate buffer 

do not stand in contact with 

rubber or plastic tubing as 

material is leached from these 

substances that can cause 

serious errors in the analysis. 

In this laboratory, the rea- 
gents are allowed to flow in 

glass tubing with only very 

short connections of plastic or 

rubber tubing. The silica 

cells are cleaned before each 

analysis with acid-alcohol 

cleaning solution and rinsed with distilled water. 

Determine the absorbancy of a "basic mix" at 270 and 290 milli- 
ticrons after diluting 1 milliliter with 100 milliliters of pH. 5 acetate 
iflfer. Subtract the absorbancies of the basic mix from the absorb- 
icies of the sample. Determine the concentrations from a 




240 26O 280 300 320 34O 

Wovlength m M 

Fig. 1 Typical absorption curves. 

A, Elon, concentration 5 grams per 
liter. 

B, hydroquinone, concentration 5 
grams per liter. 

C, Elon and hydroquinone, concen- 
tration 5 grams per liter. 



272 



REES AND ANDERSON 



September 



calibration grid as is shown in Fig. 2 or by calculation using equations 
such as (2) and (3). 

DETERMINATION OF ABSORBANCY INDICES 

Prepare mixes containing all the mix ingredients with the exception 
of hydroquinone, using concentrations of Elon covering the expected 
range. Dilute 1 milliliter of each of the mixes with 100 milliliters of 
pH. 5 acetate buffer and determine the absorbancies at 270 and 290 
millimicrons. 

In the same manner, prepare mixes containing hydroquinone but no 
Elon and determine their absorbancies at 270 and 290 millimicrons 
after dilution with pH. 5 acetate buffer. 

Prepare a basic mix. Dilute with the acetate buffer and de- 
termine the absorbancies at 270 and 290 millimicrons. Subtract 

the absorbancies of the 
basic mix from the absorb- 
ancies of each of the 
standard mixes containing 
Elon or hydroquinone and 
determine the "absorbancy 
indices" 11 according to the 
equation 




A a 
a *=bC> 



(1) 



where 



0.22 0.24 0.26 0.28 0.30 0.32 0.34 036 0.38 

Absorbancy at 270 m M 

Fig. 2 Typical calibration grid. 



a s4 = absorbancy 
indices 

A = absorbancy 
of sample 

b = length of 
solution 
path 

C = concentra- 
tion* of 
Elon or 
hydro- 
quinone. 



* The absorbancy indices in tihis paper have, for convenience, been calculated 
expressing the concentrations a|s the concentrations of Elon and hydroquinone in 
the original developer solution. Since the cells used throughout this work had 
solution paths of 1.000 == 0.005 centimeter, the length (b) in (1) has been assumed 
as unity and constant. 



1949 



PHOTOGRAPHIC DEVELOPERS 



273 



In Table I, a series of calibration mixes is shown. The absorbancies 
in the table represent the absorbancies after each was corrected for 
the absorbancy of the basic mix. 

TABLE I 
ABSORBANCY INDICES* 



Elon, 










Grams per Liter 


A 290 mu 


ai 


A- 270 mj* 


a, 3 


6.00 


0.058 


0.010 


0.425 


0.071 


6.00 


0.057 


0.010 


0.426 


0.071 


4.02 


0.039 


0.010 


0.286 


0.071 


4.00 


0.042 


0.010 


0.284 


0.071 


3.00 


0.030 


0.010 


0.217 


0.072 


2.00 


0.021 


0.010 


0.141 


0.071 


2.00 


0.022 


0.011 


0.141 


0.071 


1.00 


0.011 


0.011 


0.070 


0.070 




Avg. 


0.010 


Avg. 


0.071 


Hydroquinone, 










Grams per Liter 


^290 mit 


a s2 


^4.270 mft 


S 4 


6.00 


1.361 


0.227 


0.494 


0.082 


6.00 


1.355 


0.226 


0.492 


0.082 


5.00 


1.129 


0.226 


0.410 


0.082 


5.00 


1.129 


0.226 


0.410 


0.082 


4.00 


0.910 


0.227 


0.333 


0.083 


2.11 


0.479 


0.227 


0.175 


0.083 




Avg. 


0.226 


Avg. 


0.082 



* The slit widths used for the analyses were 0.43 mm at 270 millimicrons and 
0.36 mm at 290 millimicrons, corresponding to spectral bandwidths of 1.3 and 1.4 
millimicrons, respectively. The absorbancy indices have been found valid for use 
in analyses on three different Beckman Spectrophotometers. 



CALCULATION AND USE OF EQUATIONS 

One method of calculating the concentration of Elon and hydro- 
quinone is to use equations derived from the fundamental relationship 
given in (1). 



= 



~T 



Introducing the absorbancy indices from Table I, the following equa- 
tions are obtained for each wavelength : 



274 REES AND ANDERSON September 

A m = 0.071C E lon + 0.082C h ydro q uinone 
.4 290 = 0.010C E lon + 0.226C h ydro q uinone. 

The transformation of these equations is straightforward and yields 
the following equations: 

CEIOD = 14.84^270 - 5.39^290 (2) 

Chydroquinone = 4.66^290 ~ 0.66^270- (3) 

It must be remembered that (2) and (3) are general equations. Any 
absorbancy correction due to the blank must be subtracted before the 
concentrations of Elon and hydroquinone are calculated. 

PREPARATION AND USE OF CALIBRATION GRID 

Choose the lowest combination of Elon and hydroquinone expected 
(such as point A in Fig. 2 where concentration of Elon is 2.00 grams 
per liter and concentration of hydroquinone is 1.00 gram per liter) and 
calculate the total absorbancy at each wavelength as follows using (1). 

At 270 millimicrons: 

Absorbancy of Elon = a s3 C = 0.071X2.00 = 0.142 

Absorbancy of hydroquinone = a s4 C = . 082 X 1 . 00 = 0.082 

Total absorbancy at 270 millimicrons = . 224 
At 290 millimicrons: 

Absorbancy of Elon = a si C = 0.010 X 2.00 = 0.020 

Absorbancy of hydroquinone = a^C = 0.226 X 1.00 = 0.226 

Total absorbancy at 290 millimicrons = 0.246 

Plot the two total absorbancies (as point A in Fig. 2) which repre- 
sent an Elon concentration of 2.00 grams per liter and a hydroquinone 
concentration of 1.00 gram per liter. Compute Points B, C, and D in a 
similar manner. Draw lines through these four points which represent 
the outer limits of the grid. To complete the grid, subdivide each side 
of the parallelogram into the number of parts represented by the range 
in concentration. Increments of 0.1 gram have been found practical. 

It is thus possible to determine the concentration of both Elon and 
hydroquinone simultaneously when the absorbancy of a sample at 
each wavelength is known. 

For example : Assume that the following absorbancies (each cor- 
rected by subtracting the absorbancy of the basic mix) were obtained 
during an analysis of a developer ; the absorbancy at 270 millimicrons 
was 0.280, and at 290 millimicrons was 0.360. 



1949 



PHOTOGRAPHIC DEVELOPERS 



275 



These two absorbancies fix the point X on Fig. 2, which corresponds 
to an Elon concentration of 2.24 grams per liter and a hydroquinone 
concentration of 1.47 grams per liter. 

ANALYSIS OF USED DEVELOPERS 

Extraction of Elon and Hydroquinone with Ethyl Acetate 

Preliminary investigations showed that Elon and hydroquinone 
could be completely extracted from a developer solution at pR 8.0 to 
8.5 by the use of a solvent such as 
ethyl acetate. Ethyl acetate was 
chosen because of its low toxicity, 
small fire hazard, and its relatively 
low absorbancy in the region of 270 
to 290 millimicrons. 

Extraction of Oxidation Products 

Hydroquinone monosulfonate, 
quinhydrone, quinone, and Elon 
monosulfonate were selected as 
compounds that exist or would be 
converted into compounds that 
might exist in a used developer 
solution. 12 

A mix was prepared containing 
3.88 grams per liter of sodium hy- 
droquinone monosulfonate and no 
Elon or hydroquinone. The ab- 
sorption curves were determined be- 
fore and after extraction as shown 
in Fig. 3, curves A and B. Curve 
B has been adjusted to compensate 
for the dilution brought about by the pH. adjustment that was neces- 
sary to insure complete extraction. It is concluded from the curves A 
and B in Fig. 3 that the amount of hydroquinone monosulfonate ex- 
tracted is negligible. The small difference between the curves may 
possibly be due to the presence of a small amount of hydroquinone in 
the sodium hydroquinone monosulfonate. 

In this study, this practice was followed for all curves obtained after 
extraction. 




240 260 280 3OO 320 



with 
and 



Wavelength mp 

Fig. 3 Extraction study 
hydroquinone monosulfonate 
hydroquinone. 

A, hydroquinone monosulfonate. 

B, solution A after extraction. 

C, solution A with hydroquinone 
added. 

D, solution C after extraction. 



276 



REES AND ANDERSON 



September 



An addition of 2.00 grams per liter of hydroquinone was made to 
the original sodium hydroquinone monosulf onate solution and the ab- 
sorption curve determined before and after extraction, as shown in 
curves C and D of Fig. 3. These curves show that hydroquinone was 
extracted quantitatively in the presence of sodium hydroquinone 
monosulf onate. 

To study the effect of quinhydrone and compounds formed by inter- 
action of quinhydrone with other compounds in a developer, a mix 
was prepared containing 2.00 grams per liter of quinhydrone and no 
Elon or hydroquinone. The absorption data are shown for the solu- 
tion before and after extraction in curves A and B in Fig. 4. One gram 

i per liter of hydroquinone was added 

to the water layer after the above 
extraction. The resulting spectro- 
photometric curve is curve C in Fig. 
4 and is noted to be virtually the 
same as curve A (which was ob- 
tained from a sample containing 
2.00 grams of the quinhydrone). 
The close similarity of curves A 
and C can be explained by the 
splitting of quinhydrone into hy- 
droquinone and another product, 
which appears to be quinone, which 
is not extracted. Extraction of 
solution C (curve C) resulted in 
curve D, which is noted to be 
nearly identical with curve B, 




260 300 

avelength m 



Fig. 4 Extraction study with quin- 
hydrone and hydroquinone. 

A , quinhydrone. 

B, solution A after extraction. 

C, solution B with hydroquinone 
added. 

D, solution C after extraction. 



showing that the added hydroquinone was extracted. 

To study the effects of quinone, a mix was prepared containing 2.00 
grams per liter of quinone and no Elon or hydroquinone. The absorp- 
tion curve of this mix before and after extraction with ethyl acetate is 
shown in curves A and B, Fig. 5. The change in absorbancy and curve 
shape is considered to be due to the presence of some quinhydrone as 
an impurity in the quinone. The addition of 2.00 grams per liter of 
hydroquinone and subsequent extraction is shown by curves C and D, 
Fig. 5. It is noted that the extraction of the hydroquinone was virtu- 
ally complete. 

To check on the extraction of Elon monosulfonate, a mix was pre- 
pared containing 1.18 grams per liter of Elon monosulf onic acid and 



1949 



PHOTOGRAPHIC DEVELOPERS 



277 



no Elon or hydroquinone. The absorption curves of this mix before 
and after extraction are shown in curves A and B, Fig. 6. There is 
some change in curve shape but in view of the close agreement at 270 
and 290 millimicrons, it is probable that only a very small error, if 
any, would be introduced into the analysis of Elon and hydroquinone 
by this difference. Elon (2.00 grams per liter) was then added. Curve 
C, Fig. 6, shows the resulting absorption curve. The sample was then 
extracted. Curve D, Fig. 6, shows that the Elon was extracted quanti- 
tatively in the presence of Elon 
monosulfonate. 

From the above results obtained 
in the extraction studies of hydro- 
quinone monosulfonate, quinone, 
and Elon monosulfonate, the ex- 
traction of a used tank sample 
with ethyl acetate would remove 
only Elon and hydroquinone. In 
the case of quinhy drone (i.e., 
semiquinone-type compounds) , 
however, approximately half of 
the material present is probably 
extracted as hydroquinone. 



Procedure 




280 30O 320 

Wavelength m/i 



Fig. 5 Extraction study with qui- 
none and hydroquinone. 

A, quinone. 

B, solution A after extraction. 

C, solution A with hydroquinone 
added. 

D, solution C after extraction. 



Pipet a 25-milliliter sample of the 
used developer into a 125-milliliter 
separatory funnel and add 3 drops 
of phenolphthalein. Add drop wise 
7 normal sulfuric acid until the in- 
dicator turns colorless. (The result- 
ing solution should have a pB. of 
8.0 to 8.5.) Record the volume of acid added. 

Extract three times with 25-milliliter portions of water-saturated 
ethyl acetate (75 milliliters altogether), discarding the ethyl acetate 
layer each time. Dilute 1.00 milliliter of the extracted developer with 
100 milliliters of pH 5 acetate buffer and determine the absorbancy at 
290 and 270 millimicrons. Correct these absorbancies for the volume 
change by using the following formula : 



(absorbancy) (25 + ml 7N H 2 SO 4 ) 
(25) 



corrected absorbancy. 



278 



REES AND ANDERSON 



September 




260 280 300 320 
Wavelength m M 

dy w 
monosulfonate and Elon. 

A, Elon monosulfonate. 

B, solution A after extraction. 

C, solution A with Elon added. 

D, solution C after extraction. 



Dilute l.OOmilliliter of theunex- 
tracted developer with 100 milli- 
liters of acetate buffer and deter- 
mine the absorbancies at 270 
millimicrons and 290 millimicrons. 
Subtract the corrected absorb- 
ancies after extraction from the 
absorbancies before extraction and, 
using these differences, determine 
the concentration of Elon and 
hydroquinone from the grid or by 
calculation from the equations. 

This extraction procedure should 
be checked on a basic mix in order 
to determine if the ethyl acetate is 
extracting any material in addition to Elon and hydroquinone. If 
this is the case, a blank value should be subtracted from the ab- 
sorbancies before referring to the grid. 

Separation of Elon and Hydroquinone from Oxidation Products 

A mix was prepared containing 
6.00 grams per liter of Elon and 3.00 
grams per liter of hydroquinone. 
Exposed film was processed in this 
developer solution until the Elon 
concentration had dropped to 5.51 
grams per liter and the hydroqui- 
none to 2.48 grams per liter. The 
absorption curve of the extracted 
developer was determined and cor- 
rected for the dilution due to the 
sulfuric acid which had been added. 
The absorption curve of the devel- 
oper solution before extraction was 
also determined. The difference 
between these two curves was ob- 
tained and the result is shown in 
Fig. 7. If the procedure extracts 
Elon and hydroquinone only, and 
in the amounts as shown by the 




240 260 280 300 320 340 

Wavelength m>i 

Fig. 7 Absorption curve of ex- 
tracted material compared to the 
absorption curve of Elon and hydro- 
quinone. 

O, extracted material from used 
solution; A, hydroquinone plus Elon 
in fresh solution. 



1949 PHOTOGRAPHIC DEVELOPERS 279 

analysis of the used developer, then this curve should be identical with 
the curve of Elon and hydroquinone at these concentrations (i.e., 5.51 
grams per liter of Elon and 2.48 grams per liter of hydroquinone). 

Accordingly, a fresh developer was prepared with Elon concentra- 
tion at 5.51 grams per liter and hydroquinone concentration at 2.48 
grams per liter. The absorption curve of this mix is shown in Fig. 7. 
The close similarity of these two curves shows that the material ex- 
tracted by the ethyl acetate was Elon and hydroquinone. 

The results of this experiment show that the presence of the oxida- 
tion products of Elon and hydroquinone had no measurable effect 
upon the analysis. Other developer solutions which have contained 
larger and smaller amounts of oxidized Elon and hydroquinone have 
been analyzed, and it seems likely that large variations in the amount 
of oxidized material do not markedly affect the determination. 

EFFECT OF BUFFER pR UPON THE ANALYTICAL RESULTS 

The pH. of the acetate buffer was varied by changing the ratio of so- 
dium acetate and acetic acid, and the absorbancy indices of Elon 
and hydroquinone determined. The results are shown in Table II and 



TABLE II 
CHANGE IN ABSORBANCY INDICES WITH CHANGE IN pH OF BUFFER 



Elon . 


' Hydroquinone - 


P H 


290 m/i 


270 rn/z 


290 HIM 


270 mju 


4.96 


0.009 


0.071 


0.022 


0.081 


5.05 


0.010 


0.071 


0.022 


0.080 


5.17 


0.013 


0.070 


0.022 


0.081 


5.42 


0.019 


0.068 


0.022 


0.082 



TABLE III 
EFFECT OF pH OF BUFFER 



pH of Buffer 


Hydroquinone, 
Grams per Liter 


Elon, 
Grams per Liter 


4.90 
4.99 
5.08 


2.89 
2.93 
2.98 


6.12 
5.97 
5.95 



280 REES AND ANDERSON September 

it is evident that the buffer pR must be maintained at pR 5.00 0.02 
to insure reasonable constancy for the absorbancy index of Elon. 

Actual trials in which the pH. of the buffer was changed are given 
in Table III. Any change in absorbancy of Elon will, of course, affect 
both the Elon and hydroquinone results. 

EFFECT OF TEMPERATURE UPON THE ANALYTICAL RESULTS 

The temperature of the diluted solution should be maintained 
within a few degrees of the temperature at which the absorbancy in- 
dices were determined. This is shown in Table IV in which the varia- 
tion of Elon and hydroquinone is shown for change in temperature. 



TABLE IV 
EFFECT OF TEMPERATURE UPON ANALYTICAL RESULTS 



Temperature, C. 


Elon, 
Grams per Liter 


Hydroquinone, 
Grams per Liter 


15 
23 
33 


6.28 , 
6.15 
6.10 


2.95 
3.02 
3.06 



PRECISION AND ACCURACY 

Fresh Developers 

A series of developer solutions was prepared, in which known 
amounts of Elon and hydroquinone were used in making the solutions. 
These solutions were analyzed using the procedure for the analysis of 
fresh developers and the results obtained are shown in Table V. 

The data of these analyses were tested by the method proposed by 
Youden. 13 A plot was prepared in \vhich the mixed values were 
plotted along the abscissa and the analysis values plotted along the 
ordinate. The best straight line was then calculated to fit these 
points. From this line, the slope and intercept were determined. 

The results of the statistical study of the hydroquinone results in 
the range 2.00 to 6.00 grams per liter showed that the slope was 
0.989, which was not significantly different from unity, and that the 
extrapolated intercept was 0.033, which was not significantly different 
from zero grams per liter. The standard deviation in terms of individ- 
ual analyses was 0.041 gram of hydroquinone per liter. 



1949 



PHOTOGRAPHIC DEVELOPERS 



281 



TABLE V 
ANALYSIS OF DEVELOPERS BY THE METHOD FOB FRESH DEVELOPERS 

Mix Concentration, Analysis, Deviation, 

Grams per Liter Grams per Liter Grains per Liter 

[ix No. Hydroquinone- Elon Hydroquinone Elon Hydroquinone Elon 



A 


6.00 


6.00 


5.98 


6.05 


-0.02 


+0.05 








5.90 


6.02 


-0.10 


+0.02 


B 


6.00 


6.00 


5.95 


6.00 


0.05 










5.94 


6.05 


-0.06 


+0.05 


C 


4.00 


4.00 


4.10 


3.98 


+0.10 


-0.02 








4.10 


3.98 


+0.10 


-0.02 


D 


4.00 


4.00 


3.97 


4.02 


-0.03 


+0.02 








3.97 


4.02 


-0.03 


+0.02 


E 


4.00 


4.00 


3.92 


3.95 


-0.08 


-0.05 








3.92 


3.98 


-0.08 


-0.02 


F 


4.00 


4.00 


4.02 


4.00 


+0.02 










4.02 


3.98 


+0.02 


-0.02 


G 


4.00 


4.00 


4.00 


4.00 












3.99 


4.02 


-0.01 


+0.02 


H 


4.00 


4.00 


4.00 


3.85 




0.14 








4.00 


3.95 




-0.05 


I 


4.00 


4.00 


4.04 


4.05 


+0.04 


+0.05 








4.05 


4.15 


+0.05 


+0.15 


J 


3.00 


6.00 


3.03 


5.98 


+0.03 


. -0.02 








3.04 


6.05 


+0.04 


+0.05 


K 


3.00 


6.00 


2.97 


6.08 


-0.03 


+0.08 








2.97 


6.08 


-0.03 


+0.08 


L 


3.00 


6.00 


2.98 


6.04 


-0.02 


+0.04 








2.98 


6.05 


-0.02 


+0.05 


M 


3.00 


6.00 


3.03 


6.00 


+0.03 










3.01 


6.08 


+0.01 


+0.08 


N 


3.00 


6.00 


3.00 


6.00 












2.98 


6.05 


-0.02 


+0.05 


O 


3.00 


6.00 


3.02 


6.02 


+0.02 


+0.02 








3.00 


6.00 






P 


3.00 


6.00 


3.02 


6.02 


+0.02 


+0.02 








3.03 


6.05 


+ k 0.03 


+0.05 


Q 


2.48 


5.51 


2.47 


5.48 


-0.01 


-0.03 








2.47 


5.45 


-0.01 


-0.06 


R 


2.19 


5.75 


2.19 


5.90 




+0.15 








2.19 


5.90 




+0.15 


S 


2.00 


2.00 


1.97 


1.98 


-0.03 


-0.02 








1.97 


1.98 


-0.03 


-0.02 



282 REES AND ANDERSON September 

An identical study of the Elon results in the range 2.00 to 6.00 
grams per liter in Table V showed that the slope was 1.019 and the in- 
tercept was 0.075 gram per liter, and that these results were signifi- 
cantly different from unity for the slope and zero for the intercept. 
Cross-checks on absorbancy indices and rechecks of blank values indi- 
cate that these factors were not responsible for the deviation of the in- 
tercept from zero and the slope from unity. These differences may be 
caused by unknown factors related to the mixing procedure and the 
standing time before analysis. Future work in the range 0.00 to 2.00 
grams per liter may shed light on this subj ect . The standard deviation 
in terms of individual analyses was 0.055 gram of Elon per liter. 

It is apparent in the data in Table V that the deviation between 
duplicates is much less than the deviation between successive mixes. 
This deviation was studied and the data also show that almost all of 
the deviation of a single analysis as calculated by Youden's method is 
because of the variability between mixes. The standard deviation 
between duplicate analyses of the same mix was 0.003 gram per liter 
for hydroquinone and 0.007 gram per liter for Elon. 

Used Developers 

A series of developer solutions was prepared, in which known con- 
centrations of Elon and hydroquinone were used in making the solu- 
tion . These solutions were analyzed using the procedure for the analy- 
sis of used developer solutions and the results are shown in Table VI. 

These data were tested using Youden's method in the same manner 
as was used for the fresh developers. The results of the study showed 
that the slope for the hydroquinone analysis was not significantly dif- 
ferent, from unity. However, the intercept was 0.050 gram per 
liter, which was significantly different from zero. In nearly all cases, 
the amount of hydroquinone which was extracted was less than the 
amount put into the mix. This indicates that a portion of the hydro- 
quinone was oxidized during the mixing process or that the extraction 
was not complete. The amount of extractable hydroquinone de- 
creases on standing, and it seems probable that the principal factor 
responsible is oxidation. This is in accordance with the oxidation 
mechanism described- recently by Levenson. 9 The standard 
deviation in terms of individual analyses was 0.039 gram per liter of 
hydroquinone. 

The results of the Elon study showed that both the slope and inter- 
cept were not significantly different from unity and zero, respectively. 



1949 PHOTOGRAPHIC DEVELOPERS 283 

TABLE VI 
ANALYSIS OF DEVELOPERS BY THE METHOD FOR USED DEVELOPERS 



Mix Concentration, Analysis, 

Grams per Liter Grams per Liter 

Mix No. Hydroquinone Elon Hydroquinone Elon 



Deviation, 

Grams per Liter 

Hydroquinone Elon 



A 


6.00 


6.00 


5.96 


5.70 


-0.04 


-0.30 




6.00 


6.00 


5.98 


5.80 


-0.02 


-0.20 


B 


6.00 


0.00 


5.88 


0.05 


-0.12 


+0.05 




6.00 


0.00 


5.93 


05 


-0.07 


+0.05 


C 


4.00 


4.00 


4.03 


3.85 


+0.03 


-0.15 




4.00 


4.00 


4.03 


3.85 


+0.03 


-0.15 




4.00 


4.00 


3.94 


4.00 


-0.06 






4.00 


4.00 


3.93 


3.97 


-0.07 


-0.03 


E 


3.00 


6.00 


2.97 


6.05 


-0.03 


+0.05 




3.00 


6.00 


2.95 


6.08 


-0.05 


+0.08 


F 


3.00 


6.00 


2.94 


5.98 


-0.06 


-0.02 




3.00 


6.00 


2.94 


6.00 


-0.06 




n 


3.00 


6.00 


2.95 


6.00 


-0.05 




VJ 


3.00 


6.00 


2.95 


6.02 


-0.05 


+0.02 


H 


3 00 


6.00 


2.93 


6.15 


-0.07 


+0.15 




3.00 


6.00 


2.92 


6.18 


-0.08 


+0.18 


I 


3.00 


3.00 


2.88 


2.95 


-0.12 


-0.05 




3.00 


3.00 


2.89 


2.97 


-0.11 


-0.03 


J 


' 2.48 


5.51 


2.45 


5.50 


-0.03 


-0.01 




' 2.48 


5.51 


2.45 


5.50 


-0.03 


-0.01 


K 


. 0.00 


6.00 


-0.05 


6.08 


-0.05 


+0.08 


'.' 


0.00 


6.00 


-0.05 


6.08 


-0.05 


+0.08 



The standard deviation in terms of individual analyses was 0.114 
gram per liter of Elon. 

The data in Table VI also showed that the deviation between 
mixes was the contributing factor to the size of the standard deviation 
of single analyses for both Elon and hydroquinone. The standard de- 
viation between duplicate analyses of the same mix was 0.009 gram per 
liter of hydroquinone and 0.006 gram per liter of Elon, 

ACKNOWLEDGMENTS 

The authors wish to express their appreciation to Lloyd E. West for 
his helpful suggestions and criticisms throughout the course of the 
investigation, and to Grant Wernimont for his assistance in the statis- 
tical interpretation of the results. 



284 REES AND ANDERSON 

REFERENCES 

(1) E. Lehmann and E. Tausch, "Zum Chemismus der Metol-Hydrochinon- 
entwicklung," Phot. Korr, vol. 71, pp. 17-23; February, 1935. 

(2) R. M. Evans and W. T. Hanson, Jr., "Chemical analysis of an MQ de- 
veloper," J. Soc. Mot. Pict. Eng., vol. 32, pp. 307-320; March, 1939. 

(3) H. L. Baumbach, "The chemical analysis of hydroquinone, metol, and 
bromide in a photographic developer," J. Soc. Mot. Pict. Eng., vol. 33, pp. 517- 
524; November, 1939. 

(4) R. B. Atkinson and V. C. Shaner, "Chemical analysis of photographic de- 
velopers and fixing baths," /. Soc. Mot. Pict. Eng., vol. 34, pp. 485-523; May, 
1940. 

(5) R. M. Evans, W. T. Hanson, Jr., and P. K. Glasoe, "Synthetic aged de- 
velopers by analysis," J. Soc. Mot. Pict. Eng., vol. 38, pp. 188-206; February, 
1942. 

(6) John G. Stott, "The application of potentiometric methods to developer 
analysis," J. Soc. Mot. Pict. Eng., vol. 39, pp. 37-54; July, 1942. 

(7) H. L. Baumbach, "An improved method for the determination of hydro- 
quinone and metol in photographic developers," J. Soc. Mot. Pict. Eng., vol. 47, 
pp. 403-408; November, 1946. 

(8) V. C. Shaner and M. R. Sparks, "Application of methyl ethyl ketone to the 
analysis of developers for Elon and hydroquinone," /. Soc. Mot. Pict. Eng., vol. 
47, pp. 409-417; November, 1946. 

(9) G. I. P. Levenson, "Controlling the Elon-hydroquinone developer," 
British Kinematography, vol. 12, pp. 37-49; February, 1948. 

(10) G. I. P. Levenson, "Determination of Elon and hydroquinone in a de- 
veloper, An examination of Stott's method," Phot. J., vol. 87B, pp. 18-24; January- 
February, 1947. 

(11) National Bureau of Standards, Department of Commerce, "Terminology 
and Symbols for Use in Ultraviolet, Visible, and Infrared Absorptometry," Letter 
Circular LC 857, Washington, D. C., Government Printing Office, May 19, 
1947. 

(12) C. E. K. Mees, "The Theory of the Photographic Process," pp. 374-398; 
The Macmillan Company, New York, New York, 1945. 

(13) W. J. Youden, "Technique for testing the accuracy of analytical data," 
Ind. Eng. Chem., Anal. Ed., vol. 19, pp. 946-950; December, 1947. 



Lubrication of 16-mm Films* 

BY RALPH H. TALBOT 

EASTMAN KODAK COMPANY, ROCHESTER, NEW YORK 



Summary This paper describes materials suitable for the lubrication 
of 16-mm films. Wax-carbon tetrachloride formulas are given, together 
with the precautions which must be observed in using them. Slower- 
evaporating wax-isopropyl alcohol mixtures are described for use where 
additional drying space is available. By the use of these formulas, 16-mm 
films can be adequately lubricated at a material cost of $0.01 per 400 feet of 
film. 

New formulas using Freon, a rapid-drying, noninflammable solvent, of 
extremely low order of toxicity, are suggested. A suitable surface treatment 
for use with films to be run on repeater mechanisms is described. 



I. INTRODUCTION 

QEVERAL ARTICLES have appeared in this JOURNAL on the subject of 
O the lubrication of motion picture film. 1 - 2 It has become an es- 
tablished practice in most film laboratories to lubricate either the 
edges or the entire emulsion surface of 35-mm prints prior to projec- 
tion. This practice was adopted because of the difficulties encoun- 
tered when freshly processed prints were being projected for the first 
time. The gelatin in the emulsion of freshly processed film is very ad- 
herent to a hot metal surface and the adhesion of the film to the hot 
gate causes particles of gelatin to be rubbed off the film. Some of 
these particles may adhere to form a crust on the metal parts of a 
gate, and this crust will greatly increase the frictional resistance of 
the film through the gate. The result of high friction or "sticking," 
as it is referred to by projectionists, is noisy and unsteady projection 
and often damage to the film. 

The difficulties attending the projection of unlubricated 16-mm 
films are similar to those encountered in the projection of 35-mm 
prints. A freshly processed, unlubricated 16-mm film may project 
satisfactorily. This is sometimes the case if the moisture content of 
the film is low and if the projector is in perfect operating condition and 
is used frequently. At higher moisture contents of the film, either as 
the result of insufficient drying or of the high relative humidity of the 

* Presented April 8, 1949, at the SMPE Convention in New York. 

SEPTEMBER, 1949 JOURNAL OF THE SMPE VOLUME 53 285 



286 TALBOT September 

atmosphere, and with projectors infrequently used and not in ex- 
cellent repair, "sticking" in the gate is liable to occur. In certain 
cases, an unsteady picture and distorted sound will result. In addi- 
tion, there may be abrasion marks through the center of the row of 
perforations and along one or both sides of the sound track. If the 
"sticking" is severe, loss of the lower loop usually will occur and, if 
projection is continued, the film may become damaged be3^ond repair. 
Thus, for good operation, 16-mm films require adequate lubrication 
just as do 35-mm prints. 

There is some dissimilarity, however, between the methods of lubri- 
cation used on 35-mm film and those on 16-mm film. Edge-waxing is 
the method frequently used throughout the industry for the lubrica- 
tion of 35-mm prints. In this method a band of low-melting paraffin 
is applied from a solvent to the centers of both rows of perforations on 
the emulsion side. The Eastman Kodak Company has employed a 
modification of this method for 16-mm "customers' originals," both 
black-and-white and color, since 1928. For 16-mm films, there is 
used a very dilute solution of pure mineral oil in carbon tetrachloride. 

With the advent of 16-mm sound prints it was suggested that the 
application of mineral oil on the sound-track side of the film be omitted 
so as not to impair the sound quality. Sticking was frequently en- 
countered as the result. A new method, therefore, was sought which 
would ensure adequate lubrication of the sound-track side as well as 
of the perforated side. Over-all lubrication of the emulsion surface 
appeared to be the solution of the problem. 

II. OVER-ALL WAX LUBRICATION OF 16-MM FILMS 

Extremely thin coatings of certain waxes over the entire emulsion 
surface were found to be ideal. Each of these waxes forms a continu- 
ous transparent layer over the entire surface, providing excellent lu- 
brication and some slight amount of scratch protection as well. 

A . Waxes from Carbon Tetrachloride 

Carbon tetrachloride has long been used as a solvent for waxes and 
oils. It is the main constituent of many film-treating and film-clean- 
ing formulas. It evaporates rapidly, is noninflammable, and inexpen- 
sive. It has, however, one serious drawback, i.e., the toxicity of its 
vapors. It has been claimed that it is unhealthy to work in an atmos- 
phere in which the odor of carbon tetrachloride can be detected by the 



1949 LUBRICATION OF FILMS 287 

aid of the unfatigued nose. Carbon tetrachloride can be used if pre- 
cautions are taken to prevent its vapors from escaping into the work- 
room air even in small amounts. 

If there is room inside the drying cabinet, between the point of dry- 
ness of the film and the take-up reel, for the installation of the lubri- 
cating device, this section of the cabinet can be blocked off and the 
carbon tetrachloride vapors drawn off to the outside of the building 
with the aid of an auxiliary fan. Such a system is in operation in sev- 
eral laboratories. An apparatus for the continuous application of wax 
solutions to film is shown in Fig. 1. 




Fig. 1 Roller- wick applicator for wax solutions. 

The apparatus consists of a plush-covered roll which is driven 
slowly, generally in a direction opposite to that of the film, by an alter- 
nating-current motor operating through a thyratron speed-controller. 
Provision is made for maintaining a constant liquid level and for 
varying the extent of wrap of the film on the drum. In general, the 
film speed is fifty times that of the plush, but this varies somewhat 
with the lubricant used and the condition of the film. The extent of 
wrap also varies with the lubricant and the film; in general, the small- 
est amount of wrap that permits uniform coverage of the film should 
be used. 

All of the lubricants presented in the tables have been applied at a 
film speed of 100 feet per minute. This is the upper speed of the ma- 
chine and there is no apparent reason why higher speeds cannot be at- 
tained with adequate drying capacity. 



288 TALBOT September 

The best of these carbon tetrachloride-wax mixtures at their most 
suitable concentrations are given in Table I. It is a well-established 
fact that ethyl cellulose will raise the melting point and impart hard- 
ness and toughness to wax mixtures and that the mixture will have 
properties different from those of the individual components. 3 ' 4 It 
is for this reason that ethyl cellulose has been incorporated into some 
of the formulas. 

TABLE I 
CARBON TETRACHLORIDE-WAX SOLUTIONS FOR 16-MM FILM 

Max. Useful 
Per Cent 

Cone, in Film Friction, 

Wax CC1 4 Ounces 



Carnauba* 


0.03 


4.3 


Pentawax 217 1 


0.125 


4.0 


Johnson's WM 169CJ 


0.125 


3.9 


Beeswax (0.025%)-Ethyl Cellulose (0.075%) 


0.10 


4.5 



* No. 2 North Country Carnauba Wax obtained from Sprahl and Pitsch, 141 
Front Street, New York City. 

f Obtained from the Heyden Chemical Company, 393 Seventh Avenue, New 
York City. 

J Obtained from S. C. Johnson and Son, Inc., Racine, Wisconsin. 

Type T-200 Ethyl Cellulose obtained from Hercules Powder Company, Inc., 
Wilmington, Delaware. 

B. The Evaluation of Lubricants 

A good over-all application of wax to 16-mm film will leave an 
invisible coating on the film, will not pick up dust, nor show finger- 
prints, and will provide good steady projection even after the film has 
been subjected to conditions of high relative humidity. Inasmuch 
as many projectors will not project freshly processed, unlubricated 
films of high moisture content without damage to the film, either in 
respect to the scuffing off of emulsion particles, or damage to the per- 
forations, or both, these observations may serve as a means of evalua- 
tion of film lubricants. Freshly processed rolls of 16-mm film are 
treated with the lubricant to be tested, and these rolls, along with 
rolls of untreated film, are festooned in an atmosphere of high humid- 
ity, such as 70 per cent relative humidity at 70 degrees Fahrenheit for 
two hours. At the end of this time, the rolls are reeled and tested for 



1949 



LUBRICATION OF FILMS 



289 



behavior on various 16-mm projectors. Care is taken to -see that the 
projectors are in perfect working condition and that the gates of these 
projectors are cleaned with solvent-moistened plush after each test. 
Each projection is rated for steadiness of image, noise level, operation 
of film around snubbers, and for any deleterious effect on the sound 
quality. After the projection, the film is examined for scuffing of the 




Fig. 2 Film-friction recorder. 

emulsion in those areas where the film comes in contact with the metal 
parts of the projector and for any damage to the perforations. 

There is no alternative to projection for the evaluation of a film 
treatment. However, it is time-consuming, since many tests are nec- 
essary in order to verify preliminary findings. Moreover, some of 
these ratings, such as noise level and action of film about snubbers, 
are a matter of opinion and hence the ratings will vary from one ob- 
server to another. An independent method has, therefore, been de- 
veloped for the evaluation of film-lubrication processes. The samples 



290 



TALBOT 



September 



of film to be tested are drawn through a film-friction recorder, such as 
that shown in Fig. 2. The film to be tested is drawn through a gate 
at a rate of eight frames per second. The gate is loaded with a weight 
of six ounces. The film, before going to the constant-speed take-up 
reel, is passed over a float roll which registers the pull in ounces per 
single strand of film. A footage-tension recording is made by a pen 
on a slowly revolving drum. Before such a recording of tension is 
usable, it must be correlated with the behavior of the film on projec- 
tors. Fig. 3 shows the tracings made by an untreated sample of film 
and one which has been adequately lubricated. Projection tests show 
that films whose friction force lies between 2 and 5 ounces usually will 
_,_,_,,,,_._._,,,,,... ; , r-p, project satisfactorily. The upper 

limit for safe operation is about 
6 ounces. All the carbon tetra- 
chloride-wax lubricants shown in 
Table I gave films whose fric- 
tional forces were 4y 2 ounces or 
less, and all gave films of satisfac- 
tory projection performance. 

C. New Solvents for Waxes 

If ample space can be allotted 
for the lubrication operation, a 
wax solution of slower rate of 
evaporation than the carbon 
tetrachloride-wax mixture may 
be used and thus the pre- 
cautions necessary with the 
latter can be avoided. Certain waxes are sufficiently soluble in anhy- 
drous isopropyl alcohol to offer effective lubrication for 16-mm film. 
Anhydrous isopropyl alcohol is readily available, inexpensive, non- 
toxic, and almost free from explosion hazards. The evaporation rate 
of isopropyl alcohol is four times slower than that of carbon tetra- 
chloride. Examples of isopropyl alcohol-wax lubricants are given in 
Table II. 

Within recent years, a new chemical compound has appeared which 
may end the long search for a nontoxic, noninflammable, rapidly evap- 
orating solvent. This compound is Freon 113 or trichlorotrifluoro- 
ethane. It has an evaporating rate faster than that of carbon tetra- 
chloride, is completely noninflammable, and has a very low order of 




Fig. 3 Film-friction graphs of lubri- 
cated and unlubricated films. Lower 
curve is for lubricated film. 



1949 LUBRICATION OF FILMS 291 

toxicity. Freon 113 will dissolve beeswax or cetyl alcohol in concen- 
trations sufficient to provide good lubrication, as shown in Table III. 
The addition of 6.7 per cent cyclohexane will permit a greater amount 
of beeswax to be dissolved. This gives slightly better lubrication and 
yet does not materially change the nonexplosive nature of the solvent. 
At present, Freon 113 is considerably more expensive than carbon tet- 
rachloride. It should be mentioned, however, that the cost of all the 
lubricants described in this paper, with the exception of the Freon 
mixtures, is less than $0.01 per 400 feet of 16-mm film. The cost in the 
case of the Freon mixtures at the present time is approximately $0.06 
per 400 feet of 16-mm film. There is reason to believe that these Freon 
lubricants may provide the means for safe and effective film treatment. 



TABLE II 
ISOPKOPYL ALCOHOL- WAX SOLUTIONS FOB 16-MM FILM 







Max. Useful 








Per Cent 








Cone, in 








Isopropyl 


Film Friction, 




Wax 


Alcohol 


Ounces 


Beeswax (0 . 


04%)-Ethyl Cellulose(0 . 035%)* 


0.075 


2.8 


Armid HTf 




0.05 


4.2 



* Type T-200 Ethyl Cellulose obtained from Hercules Powder Company, Inc., 
Wilmington, Delaware. 

t Obtained from Armour and Company, 1335 W. 31 Street, Chicago 9, Illinois. 



TABLE III 
FREON 113- WAX SOLUTIONS FOR 16-MM FILM 





Max. Useful 






Per Cent 






Cone, in 





Wax 


Freon 113* 


Ounces 


Beeswax 


0.1 


3.5 


Cetyl Alcohol 


0.1 


4.1 


Beeswax 


0.2 (Freon 93. 3%, 


2.2 




Cyclohexane 






6.7%) 





* Obtained from Kinetic Chemicals, Inc., Wilmington, Delaware. 



292 TALBOT 

III. TREATMENT OF FILMS FOR USE ON REPEATER MECHANISMS 

Considerable attention has been given to the surface treatment of 
films intended for use on repeater mechanisms. Several types of 
these have been studied some to a considerable extent. In one in- 
stance, a film of approximately 400 feet in length was prepared as 
an instructional aid for the manufacturer's service organization. 

In the course of these investigations many types of surface treat- 
ments were studied, including several well-known products. Many of 
these film-treating processes which offered some degree of protection 
against film failure upon normal projection were found to be inade- 
quate for repeater-projection operation. It has been found that the 
simple carbon tetrachloride-carnauba wax treatment of both surfaces 
of the film gives excellent film performance on all types of repeaters, 
and this treatment has been the standard in the investigations by 
which all other treatments are judged. 

Substantially flat film is also a prerequisite for good film perform- 
ance on repeater mechanisms. Film can be made to remain flat by 
proper control of the relative humidity. No surface treatment can 
assure successful film performance on repeaters unless the film is 
maintained essentially flat. 

ACKNOWLEDGMENTS 

The film-friction recorder described in this paper was developed by 
Mr. E. Seymour, of the Development Department, at the Camera 
Works of the Eastman Kodak Company, and has been used for some 
time by Mr. John T. Parker, of the Department of Manufacturing 
Experiments, at Kodak Park Works, for studying film friction in 
cameras and projector gates. 

The author wishes to express his sincere appreciation to Dr. C. R. 
Fordyce, for his helpful suggestions and for continued guidance in the 
preparation of the paper, and to his colleague, Mr. Thomas J. Mc- 
Cleary, who aided materially in the assembly of the data presented. 

REFERENCES 

(1) J. I. Crabtree and C. E. Ives, "The lubrication of motion picture film." 
Trans. Soc. Mot. Pict. Eng., vol. 11, pp. 522-541; Number 31, 1927. 

(2) J. I. Crabtree, Otto" Sandvik, and C. E. Ives, "The surface treatment of 
sound film," /. Soc. Mot. Pict. Eng., vol. 14, pp. 275-290; March, 1930. 

(3) "Ethyl Cellulose, Properties and Uses," Hercules Powder Company, Wil- 
mington, Delaware, 1944. 

(4) H. Bennett, "Commercial Waxes, Natural and Synthetic," Chemical Pub- 
lishing Company, Inc., Brooklyn, New York, 1944. 



Proposed American Standards 
16- and 8-Mm 



THE THREE STANDARDS which appear on the following pages are 
being published for 90 days' trial and criticism. Any comment 
you may have should be addressed to the Staff Engineer at the 
Society's office, 342 Madison Avenue, New York 17, New York, 
before January 1, 1950. 

Proposed American Standard for Mounting Threads and Flange Focal 
Distances for Lenses on 16- and 8-mm Motion Picture Cameras 

During the war the Armed Services wanted to be able to use lenses 
for 16-mm cameras interchangeably between cameras of one manu- 
facturer and, if possible, between cameras of different manufacturers. 
Consequently the War Committee on photography, Z52, drew up a 
War Standard Z52. 50-1946 which specified the, mounting threads and 
registration distances for 16-mm camera lenses. 

After the war the standard was reviewed by the peacetime com- 
mittee on Motion Pictures Z22 and referred to the SMPE for revision 
and resubmittal for approval as a regular American Standard. 

Consequently in due course the Society's Technical Committee 
on 16- and 8-Mm Motion Pictures reviewed this standard and re- 
vised it so as to apply to 8-mm as well as 16-mm cameras. 

It will be noted that a second mounting thread, the 5 / 8 -hich, 32 
thread, makes the standard apply to several 8-mm cameras, whereas 
the 1-inch, 32 thread is used primarily for 16-mm cameras. The 
committee, however, did not wish to label the threads 8-mm and 16- 
mm, respectively, because there may be cases where the larger thread 
will be desirable for 8-mm cameras and, less likely, where the smaller 
thread may be useful for 16-mm cameras. 

One of the chief objects of this standard is to establish dimensions 
for the threads in cameras and on lenses that will provide the proper 
fit between the corresponding parts, thus ensuring mechanical inter- 
changeability. This is covered by the data given for Dimension A 
and by the specification of 32 threads per inch. A second object is to 
control the lengths of the threads so that the le.ns will seat properly, 
be in proper registration, and yet have enough threads in engagement 

SEPTEMBER, 1949 JOURNAL OP THE SMPE VOLUME 53 293 



294 PROPOSED AMERICAN STANDARDS September 

to hold the lens securely. This is covered by Dimension B and 
the notes that apply to it. The last note in this group indicates 
that manufacturers have already experienced some difficulty with the 
fairly recent 5 /8-inch size. This emphasizes the desirability of having 
a clear-cut standard early in the development of such equipment. 

Next, it is important to specify the distance from the lens seat to 
the plane of best focus, which is covered by Dimension C and its 
notes. This part of the standard is believed to be an advance over 
the methods sometimes used in the past. In specifying that C is 
the distance from the lens seat to the plane of the best photographic 
image, the standard makes it clear to the camera manufacturer that 
the distance is to the actual surface of the emulsion, not to some 
arbitrary plane in which the emulsion is supposed to lie. Thus in 
locating the surfaces of the gate, the camera manufacturer must 
allow for the slight bowing or buckling of the film that is almost 
always present. As the proposed standard states, this buckling 
may require a compromise setting in order to obtain the best 
average results over the whole field. 

Although not mentioned in the draft published herewith, there was 
discussion in the committee regarding the necessary compromise be- 
tween the focus that is best for a wide-open lens and the focus that is 
best when the lens is stopped down. One suggestion was that the 
setting should be made with the lens closed two stops from its wide- 
open position. Whether or not that procedure is satisfactory de- 
pends a great deal on the lens openings most commonly used. 

Finally, Dimension D of the standard provides information about 
the diameter of the lens seat, with particular reference to prevention 
of interference between the lens and the front of the camera when the 
lens seat is recessed. 

Approval of this standard will not bar the use of other methods 
of attaching lenses to motion picture cameras. Some lenses are 
mounted by means of bayonet mounts or threads of a different size. 
Furthermore, these proposed standards are obviously unsuited to 
some cameras, for example high-speed cameras with rotating prisms, 
which require considerable space between the film and the lens mount. 
The intent of this proposal is to remove the 1-inch, 32 thread and the 
Vs-inch, 32 thread from the category of "unwritten" standards and 
to associate them with the definite registration distances of 0.690 
inch and 0.484 inch, respectively. Great confusion would result if 
different cameras had the same thread, but quite different registration 



1949 PROPOSED AMERICAN STANDARDS 295 

distances. Similarly, too many sizes of mounting threads would 
limit the possibility of interchanging lenses. 

In the first discussions of the Z52 committee, a new mount with 
l 3 / 4 -inch or lV 2 -inch threads was considered because of its greater 
potential strength and rigidity. It was dropped, however, when it 
became evident that a new larger size would entail great expenditures 
of time and money for tools, and that providing adapters to accept 
the larger lenses on old cameras and the 1-inch lenses on new cameras 
would be difficult and confusing. 

In the proceedings of the committee, one or two of the dimensions 
were questioned and either changed or amended by notes. Most 
of the discussion and criticism was about the terms used for the various 
components and dimensions. As far as practicable, all these sug- 
gestions were included in the proposed standard. 

Proposed American Standard Base Point for Focusing Scales on 16-Mm 
and 8-Mm Motion Picture Cameras 

This proposed standard is also a revision of a former War Standard 
Z52.51-1946 developed under the War Procedures of the ASA for the 
use of the Armed Services. The War Standard, however, was limited 
to 16-mm motion picture cameras and so when the revision was 
undertaken by the 16- and 8-Mm Committee of the Society, it was 
believed desirable to extend this standard to apply to 8-mm cameras 
as well. This was believed desirable because many lenses are used 
interchangeably on both 16-mm and 8-mm cameras. 

The main purpose of the proposed standard is to remove all doubt 
about the point from which measurement is made when the subject, 
or object, distance is determined. Past practice had not been uniform 
in this respect. In some cases focusing scales were based on measure- 
ments made from the focal plane, but in other cases the front gauss 
point of the lens, the front of the camera, or some special index line 
engraved on the barrel of the lens was the base point. It was con- 
sidered better to settle on the focal, or film, plane because that is 
common to all cameras and lenses. Moreover, it is a plane that can 
be located readily. 

When the object distance is great, it is not necessary to specify 
the base point with great exactitude. Current lenses, however, can 
be focused on extremely short object distances. That, combined 
with their high speed results in limited depth of field. Then it is 
important to place on the camera a conspicuous index mark for the 



296 PROPOSED AMERICAN STANDARDS September 

base point, and to have it located with some precision. That is why 
the second paragraph of the standard specifies the shape of a dis- 
tinguishing index mark for the camera and states the accuracy with 
which it shall be located with respect to the film plane. 

The note suggests a way to indicate on a lens that the base point 
for its focusing scale is in the focal plane. Most lenses are engraved 
"Feet" or ' 'Inches" and there is usually room to add the words "From 
Film." Unfortunately there is no corresponding way to state this 
simply on metric lenses, in terms that will be clear to all the nation- 
alities employing the metric system. 

In the discussions by the committee, there has been no divergence 
of opinion on the location and identification of the base point. Several 
changes in the wording of the standard have been suggested, and 
some have been made, but they were merely to clarify the meaning 
and preclude misunderstanding of the terms. 

Proposed American Standard Winding of 16-Mm Sound Film 

While this is the first time the matter of winding 16-mm sound 
film has been proposed for adoption as an American Standard, it has 
been followed in practice by the film manufacturers for a number of 
years. In addition, in 1941 the SMPE recognized the method of 
designating the two types of winding by publishing an SMPE recom- 
mendation which was substantially the same as the recent proposal. 
The only difference is that two sentences of explanation have been 
added to the present draft in an effort to clarify the meaning. 

It is believed this standard fills a recognized need for a uniform way 
of designating the direction of winding of 16-mm sound film. It is 
definitely not the intent of this standard to indicate any preferred 
choice in the direction of winding since existing equipment is designed 
to use both styles. 



1949 



PROPOSED AMERICAN STANDARDS 



297 



Proposed American Standard 
Base Point for Focusing Scales on 16 Millimeter and 8 Millimeter 

Motion Picture Cameras 



Z22.74 
Sept. 1949 



1. Focusing scales for 16 millimeter and 8 millimeter motion picture cam- 
eras and associated lenses shall indicate object distances measured 
to the film plane; i.e., the zero point for the focusing scale shall be in 
the plane of the film. 

2. An index mark to indicate the film plane shall be placed on the outside 
of the camera. This mark shall consist of a circle crossed by a line having 
a length of between two and three times the diameter of the circle (see 
illustration blow). The line shall be in the plane of the film within 0.040 
inch. 




Note: One way to distinguish focusing scales made in accordance 
with this standard is to have the words "From Film" appear after 
the word "Feet" or other unit designation. 



NOT APPROVED 



298 



PROPOSED AMERICAN STANDARDS 



September 



Proposed American Standard 
for Winding of 

16-Millimeter Sound Film 



Z22.75 
Sept. 1949 



The purpose of this standard is to insure a uniform method of designating 
the direction of winding in ordering or in describing 16-millimeter sound 
film. There is no preferred direction of winding because the operation of 
existing equipment may require film wound in either direction. 

Winding "A" of 16-millimeter sound motion picture film shall have the 
perforations toward the observer when the roll is held with the outside end 
at the top, toward the right, and emulsion side in. 

Winding "B" of 16-millimeter sound motion picture film shall have the 
perforations away from the observer when the roll is held with the outside 
end at the top, toward the right, and emulsion side in. 





Winding A 
Emulsion side in 



Winding B 
Emulsion side in 



The drawings show film wound on cores. When film is wound on reels 
having square holes on one side and round holes on the other, it is under- 
stood the square hole will be on the side away from fhe observer. 



NOT APPROVED 



1949 



PROPOSED AMERICAN STANDARDS 



299 



Proposed American Standard 

Mounting Threads and Flange Focal Distances for 

Lenses on 16 Millimeter and 8 Millimeter 

Motion Picture Cameras 



Z22.76 
Sept. 1949 



Page 1 of 2 pages 



The purpose of this standard is to describe the two sizes of screw threads 
and the related flange focal distances in common use for mounting objective 
lenses on 8 millimeter and 16 millimeter motion picture cameras. The 
external thread is on the lens, and the internal thread is in the camera. 



LENS SEAT THIS SHOULDER ON 

THE LENS MOUNT REGISTERS 

ACAINST THE LENS SEAT ON THE PLANE OF 

FRONT OF THE CAMERA . BEST FOCUS 




Nominal (Major) 
Diameter of Lens 
Attaching Thread 


Threads Length from 
Per Shoulder to 
Inch End of Thread 


Flange 
Focal 
Distance 


Diameter of 
Lens Seat 


(A) 
Inch 


(B) 
Inch 


(0 
Inch 


(D) 
Inch 


0.625 
1.000 


32 0.115 
32 0.156 


0.484 
0.690 


1 .000 
1.187 



Dimension A: The American National Thread Form should be used. 

Dimensions and tolerances shall conform to those established for a 
Class 2 Fit by the National Bureau of Standards Handbook H28, Screw 
Thread Standards for Federal Services (Section V, Screw Threads of 
Special Diameters, Pitches, and Lengths of Engagement). 

Dimension B: The values given for this dimension in the above table are to 
be considered as the maximum for the lens; a little additional length, for 
clearance, should be provided in the camera. 



NOT APPROVED 



300 PROPOSED AMERICAN STANDARDS 



Proposed American Standard 

Mounting Threads and Flange Focal Distances for 

Lenses on 16 Millimeter and 8 Millimeter 

Motion Picture Cameras 



Z22.76 
Sept. 1949 



Page 2 of 2 pages 



With some lenses a section of the mount, with a diameter smaller than 
the root of the thread, necessarily extends closer to the film than is indicated 
by the above drawing. In those cases, the mechanical clearance in the camera 
must be determined individually. 

In the past, a number of lenses with the 1-inch thread had a "B" dimen- 
sion of 0.1 87 inch. This is considered to be an obsolete practice. 

Past practice has not been entirely consistent so far as the "B" dimension 
of the 0.625-inch thread is concerned; some existing cameras will not accept 
a thread longer than 0.115 inch; some lenses have been made with a 
length of 0.120 or 0.125 inch. 

Dimension C: This dimension is defined as the distance from the lens seat to 
the plane of the best photographic image. It should be determined photo- 
graphically with panchromatic film and with the camera operating 
normally. Sometimes a compromise is necessary between best central 
definition and best over-all definition. 

The tolerance acceptable for dimension "C" is dependent on the depth 
of 'focus and on a decision as to what portion of the depth can be used for 
the focus tolerance. In some cases, the tolerance is very small. For example/ 
with a 25-millimeter f/1.4 lens and a 0.001 inch circle of confusion, the 
depth of focus is 0.0014 inch; only part of this is available for the sum of 
the lens and camera focusing tolerances. 

D;'mens/on D: The values given in the table are to be considered as the maxi- 
mum diameter of the seat on the lens; the seat on the camera should 
provide clearance for these diameters. 

If any part of the lens mount has a larger diameter, it should be checked 
for mechanical interference with the camera on which- 1 it is to be used. Some 
lenses with the 1-inch thread have been made with a flange diameter of 
1.500 inches. 

Note: This standard does not apply to continuous-type motion picture 
cameras because of the type of optical system employed in these 
cameras. 



NOT APPROVED 



66th Semiannual Convention 
SOCIETY OF MOTION PICTURE ENGINEERS 

Hollywood-Roosevelt Hotel October 10-14, 1949 
Hollywood, California 


OFFICERS IN CHARGE 

EARL I. SPONABLE President 

LOREN L. RYDER Past-President 

PETER MOLE Executive V ice-President 

JOHN A. MAURER Engineering Vice-President 

CLYDE R. KEITH Editorial Vice-President 

DAVID B. JOY Financial Vice-President 

WILLIAM C. KUNZMANN Convention Vice-President 

ROBERT M. CORBIN Secretary 

RALPH B. AUSTRIAN Treasurer 

General Office, New York 

BOYCE NEMEC Executive Secretary 

HELEN M. STOTE Journal Editor 

WILLIAM H. DEACY, JR Staff Engineer 

SIGMUND M. MUSKAT Office Manager 

Chairmen of Committees for the Convention Program 

Convention Vice-President W. C. KUNZMANN 

Pacific Coast Section and Local Arrangements S. P. SOLOW 

Papers Committee Chairman N. L. SIMMONS 

Vice-Chairman, Hollywood L. D. GRIGNON 

Vice-Chairman, New York E. S. SEELEY 

Vice-Chairman, Chicago. R. T. VAN NIMAN 

Vice-Chairman, Washington J. E. AIKEN 

Vice-Chairman, Montreal H. S. WALKER 

Publicity Committee Chairman ; HAROLD DESFOR 

Vice-Chairman, West Coast Announced Later 

Registration and Information C. W. HANDLEY 

Assisted by W. L. FARLEY and R. H. DUVAL 

Luncheon and Banquet J. P. LIVADARY 

Hotel Housing and Reservations WATSON JONES 

Membership and Subscriptions LEE JONES 

West Coast Vice-Chairman G. C. MISENER 

Ladies' Reception Committee Hostess MRS. PETER MOLE 

Transportation Rail, Plane, Local HERBERT GRIFFIN 

Public-Address Equipment LLOYD T. GOLDSMITH 

Projection Program Committee 35-Mm R. H. McCuLLOUGH 

Assisted by Members of Los Angeles Projectionists Local 150 

Projection Program Committee 16-Mm H. W. REMERSCHEID, 

E. C. FRITTS 

301 



302 66TH SEMIANNUAL CONVENTION September 

GENERAL INFORMATION 

HOTEL RESERVATIONS AND RATES The Housing Committee, under 

Watson Jones, chairman, will make 

reservations for members and guests. Inform him at 1560 North Vine Street, 
Hollywood 28, California, of the accommodations you desire. He will book your 
reservations and confirm them. 

TRAVEL Make your train or plane reservations early because West Coast 
travel in October normally is quite heavy. 

PAPERS PROGRAM Authors who plan to prepare papers for presentation at 
the 66th Convention should write at once for Authors' 

Forms and important instructions to the Papers Committee member listed below 
who is nearest. Authors' Forms, titles, and abstracts must be in the hands of 
Mr. Grignon by August 15 to be included in the Tentative Program, which will 
be mailed to members thirty days before the Convention. 
N. L. SIMMONS, Chairman E. S. SEELEY, Vice-Chairman 

6706 Santa Monica Blvd. Altec Service Corp. 

Hollywood 38, California 161 Sixth Ave. 

J. E. AIKEN, Vice-Chairman New York 13 > New York 

116 N. Galveston St. R - T ' VAN NlMAN > 

Arlington, Virginia 4501 Washington Blvd. 

Chicago 24, Illinois 

LORIN GRIGNON, Vice-Chairman H. S. WALKER, Vice-Chairman 

20th Century-Fox Films Corp. 1620 Notre Dame St., W. 

Beverly Hills, California Montreal, Que., Canada 

CONVENTION GET-TOGETHER LUNCHEON The 66th Semiannual Con- 
vention Get - Together 

Luncheon for members, guests, and ladies attending the Convention will be held 
in the Blossom Room on Monday, October 10, at 12:30 P.M. There will be emi- 
nent speakers and entertainment. 

Most important Luncheon seating will only be guaranteed and assured if 
tickets have been procured prior to the Convention from W. C. Kunzmann, 
Convention Vice-President, or before 11:00 A.M. on October 10 at Registration 
Headquarters. 

Checks or money orders issued for Registration fees, Luncheon, or Banquet 
tickets should be made payable to W. C. Kunzmann, Convention Vice-President, 
and not to the Society. 

BANQUET AND COCKTAIL The Convention Cocktail Hour for holders 
HOUR of Banquet tickets will be held in the Redwood 

Room on the mezzanine floor, on Wednesday evening, October 12, between 7: 15 
P.M. and 8:15 P.M. 

The Banquet (dress optional) will be held in the Blossom Room on Wednesday 
evening, October 12, promptly at 8:30 P.M. 

There will be entertainment and dancing, and at this time the Annual Awards 
will be made. 

NOTE: Tables for the Banquet can be reserved at Registration Headquarters 
prior to noon on October 12. 



1949 



66TH SEMIANNUAL CONVENTION 



303 



LADIES AND GUESTS Members are encouraged to invite their friends to 
attend the Convention. There will be eleven Tech- 
nical Sessions open to all who wish to be on hand, and for the ladies who accom- 
pany their husbands, the Ladies' Committee is arranging a week of sight-seeing 
and special events. The Ladies' Registration Headquarters will be located in 
parlor suite 420-421 in the Hollywood-Roosevelt Hotel. The ladies attending 
the Convention should register and receive their badges, identification cards, 
and programs. Mrs. Peter Mole will serve as Hostess. 

RECREATION The identification cards issued to members and guests who 
register for the Convention will permit them to attend Grau- 
man's Chinese and Vogue Theaters of the Fox West Coast Circuit, the Holly- 
wood Paramount, the Pantages, and Warner Theaters, all of which are located 
on Hollywood Boulevard and near the hotel. Convention Headquarters will 
have a wealth of information on places to visit in or near the Los Angeles area. 

TENTATIVE PROGRAM 



Monday, October 10, 1949 

9 : 30 A.M. REGISTRATION 

Convention Headquar- 
ters 
12:30 P.M. LUNCHEON 

Blossom Room 
3:00 P.M. BUSINESS AND TECHNICAL 

SESSION 
Blossom Room 
8:00 P.M. COLOR SESSION 
Blossom Room 

Tuesday, October 11, 1949 

9: 30 A.M. REGISTRATION 

Convention Headquar- 
ters 
10:00 A.M. COLOR SESSION 

Blossom Room 
2:00 P.M. COLOR SESSION 

Academy Theater 
8:00 P.M. COLOR SESSION 

Academy Theater 

Wednesday, October 12, 1949 

9: 30 A.M. REGISTRATION 

Convention Headquar- 
ters 

10: 00 A.M. HIGH-SPEED PHOTOG- 
RAPHY SESSION 
Aviation Room 



2:00 P.M. HIGH - SPEED PHOTOG- 
RAPHY SESSION 

Aviation Room 
7:15 P.M. COCKTAIL HOUR 

Redwood Room 
8:30 P.M. BANQUET 

Blossom Room 

Thursday, October 13, 1949 
10: 30 A.M. HIGH - SPEED PHOTOG- 
RAPHY SESSION 
Aviation Room 
2:00 P.M. FIELD TRIP TO MOUNT 

WILSON 

Television Transmitters 
and 100-inch Tele- 
scope 
8:00 P.M. TELEVISION SESSION 

Carnegie Assembly Hall, 
Mount Wilson Obser- 
vatory 

Friday, October 14, 1949 
10: 00 A.M. SYMPOSIUM ON MAGNETIC 

RECORDING 
Blossom Room 

2:00 P.M. MOTION PICTURE PRO- 
DUCTION SESSION 
Blossom Room 
8:00 P.M. STUDIO-LIGHTING SESSION 

Blossom Room 
ADJOURNMENT 



Proposed New Constitution 
and Bylaws 



A RECENT ACTION taken by the Society's Board of Governors re- 
quires that certain matters be submitted to the Society members 
for their consideration and decision. A special committee, which 
the then incumbent President Loren Ryder appointed on October 
24, 1948, considered the advisability of acknowledging in some formal 
way the growing interest of the Society and its members in the 
relatively new field of television. On April 3, 1949, the Committee 
reported to the Board of Governors that agreement had been reached 
only one member dissenting on a proposal to change the name of 
the association from * 'Society of Motion Picture Engineers" to 
' 'Society of Motion Picture and Television Engineers." This change 
of name requires a change in the Constitution. 

Another special committee was also appointed by the then Presi- 
dent Loren Ryder, on January 23, 1947, to study the Society's funda- 
mental purposes and its methods of operation. 

This Committee was also asked to reconcile certain inconsistencies 
that exist between the Constitution and Bylaws, and in addition to 
reword certain paragraphs, or articles, which were obscure or 
redundant. 

The Board has endorsed these proposals and now, as required by 
Article VII of the Constitution, the proposed name change, with the 
other recommended changes, will be submitted for discussion by the 
members at the Annual Meeting of the Society (which is a part of 
the Fall Convention) ; and then, immediately following the meeting, 
the proposals, with a letter ballot and a transcript of the meeting 
discussion, will go to all voting members for their formal action. 

The new Constitution, which has been proposed, is published here 
in advance of its distribution to the voting membership, since it is of 
interest to all the Society members. Comparison between the old 
and the new Constitutions may be readily made by referring to page 
463 of the JOURNAL for April, 1949. The change-of-name question 
will be included with the Constitution letter ballot, which will be 
mailed shortly after the Fall Convention. 
304 SEPTEMBER, 1949 JOURNAL OF THE SMPE VOLUME 53 



PROPOSED NEW CONSTITUTION 305 

The important proposed changes in the Constitution can be sum- 
marized briefly as follows : 

Article I provides for the change of name. 

Article II covers the addition of the television art to the scope of the 
Society. 

Article III now covers "Meetings," formerly covered by Article VI, 
and is reworded to be more explicit. 

Article IV has been reworded for clarity. 

Article V assigns the executive duties of the President in his 
absence to the Executive Vice-President, instead of to the Past- 
President, as is now the case, and has been further reworded for 
clarity. 

Article VI is new and defines "Sections." 

Article VII provides for twelve elected Governors, allowing the 
Atlantic Coast, Central, and Pacific Coast Sections each to be repre- 
sented by four elected Governors. Previously, representation of the 
Central Section was not assured. 

Article VIII clarifies former Article VII and deals with amend- 
ment procedures. 

The work of the Committee on the revision of the Bylaws is not as 
yet complete; substantial progress has been made, however, and it is 
expected that the proposed revision will be printed as amendments 
to the Bylaws in the issue of the JOURNAL immediately preceding 
the 67th Semiannual Convention to be held at the Drake Hotel in 
Chicago, April 24-28, 1950, at which meeting formal action may then 
be taken on their proposals. 

It is suggested that all voting members who find it possible to attend 
the 66th Convention in Hollywood from October 10 to October 14 
should do so and should be on hand for the Business Meeting at which 
these changes will be discussed. 



Proposed New Constitution 

of the Society of Motion Picture Engineers 



CONSTITUTION 



a Past-President, an Engineering Vice- 
President, an Editorial Vice-President, 
a Financial Vice-President, a Conven- 
tion Vice-President, a Secretary, and a 
Treasurer. 

The term of office of all elected 
officers shall be for a period of two 
years. 

The President shall not be eligible to 
succeed himself in office. 

At the conclusion of his term of office 
the President automatically becomes 
Past-President. 

Under conditions as set forth in the 
Bylaws, the office of Executive Vice- 
President may be vacated before the 
expiration of his term. 

A vacancy in any office shall be filled 
for the unexpired portion of the term in 
accordance with the Bylaws. 

Article VI 
SECTIONS 

Sections may be established in 
accordance with the Bylaws. 

Article VII 

BOARD OF GOVERNORS 
The Board of Governors shall con- 
sist of the President, the Past-Presi- 
dent, the five Vice-Presidents, the Secre- 
tary, the Treasurer, the Section Chair- 
men, and twelve elected Governors . An 
equal number of these elected Gover- 
nors shall reside within the areas in- 
cluded in the Eastern time zone; the 
Central time zone; and the Pacific 
and Mountain time zones. The term 
of office of all elected Governors shall 
be for a period of two years. 
SEPTEMBER, 1949 JOURNAL OF THE SMPE VOLUME 53 



Article I 

NAME 

The name of this association shall be 
SOCIETY OF MOTION PICTURE 
AND TELEVISION ENGINEERS. 

Article II 

OBJECTS 

Its objects shall be: Advancement in 
the theory and practice of engineering 
in motion pictures, television, and the 
allied arts and sciences; the standard- 
ization of equipment and practices em- 
ployed therein; the maintenance of a 
high professional standing among its 
members; and the dissemination of 
scientific knowledge by publication. 

Article III 

MEETINGS 

There shall be an annual meeting 
and such other regular and special 
meetings as provided in the Bylaws. 

Article IV 

ELIGIBILITY FOR MEMBERSEIIP 
Any person of good character is 
eligible to become a member in any 
grade for which he is qualified in ac- 
cordance with the Bylaws. 

Article V 

OFFICERS 

The officers of the Society shall be a 
President, an Executive Vice-President, 
306 



PROPOSED NEW CONSTITUTION 



307 



Article VIII 
AMENDMENTS 

This Constitution may be amended 
as follows: Amendments may originate 
as recommendations within the Board 
of Governors, or as a proposal 
to the Board of Governors, by 
any ten members of voting grade; 
when approved by the Board of Gover- 
nors as set forth in the Bylaws, the pro- 
posed amendment shall then be sub- 
mitted for discussion at the annual 
meeting or at a regular or special meet- 
ing called as provided in the Bylaws. 
The proposed amendment, together 



with the discussion thereon, shall then 
be promptly submitted by mail to all 
members qualified to vote, as set forth 
in the Bylaws. Voting shall be by letter 
ballot mailed with the proposed 
amendment and discussion to the vot- 
ing membership. In order to be 
counted, returned ballots must be re- 
ceived within sixty (60) days of the 
mailing-out date. An affirmative vote 
of two thirds of the valid ballots re- 
turned subject to the above time limita- 
tions, shall be required to carry the 
amendment, provided one fifteenth of 
the duly qualified members shall have 
voted within the time limit specified 
herein. 



Membership Certificates 



Would you like a certificate of your membership in the SMPE? 
Many members hang them in their offices or homes. 
They are available from Society Headquarters for $1.50. 






Society Announcements 



Committee Changes 

On pages 481-495 of the April, 1949, issue of the JOURNAL, the names of the 
members of the Society's Committees were published. Since that date, several 
changes have been made as listed below. Where there is no mention of a Com- 
mittee, it is because there have been no changes. 



Committee 

COLOR 

Add F. T. Bowditch 
HIGH-SPEED PHOTOGRAPHY 

Add C. W. Wyckoff 
HISTORICAL AND MUSEUM 
Add 
W. H. Offenhauser, Jr., 

Vice- Chairman 
G. J. Badgley 
J. A. Ball 
L. W. Bonn 
H. T. Cowling 
W. A. Jamison 
Beaumont Newhall 
Terry Ramsaye 
E. I. Sponable 
Randall Terraneau 
LABORATORY PRACTICE 
Change Address 
J. G. Stott 

Du Art Film Laboratories 
245 W. 55 St., 
New York 19, N. Y. 
PAPERS 

Add W. H. Rivers 
Delete 
G. M. Best 
P. E. Brigandi 
J. P. Corcoran 
G. R. Crane 
C. R. Daily 
Correct Address 
R. T. Van Niman 
4431 W. Lake St. 
Chicago 24, 111. 



Committee 

PRESERVATION OF FILM 

Add J. B. McCullough 
PROCESS PHOTOGRAPHY 

Add A. C. Robertson 
PROGRESS 

AddR. T. Van Niman 
Correct Address 
C. R. Sawyer 

Western Electric Co. 
175 Chambers St. 
New York 7, N. Y. 
16-MM AND 8-MM MOTION PICTURES 

AddJ, L. Forrest 
STANDARDS 

Add L. W. Davee 
TELEVISION 
Add 

Willy Borberg 
R. V. Little 

Delete Frank Goldbach 
TEST-FILM QUALITY 
Change Address 
F. S. Berman 

Movielab Film Laboratory 
619 W. 54 St. 
New York 19, N. Y. 
THEATER ENGINEERING 
Add O. P. Beckwith 
Delete A. G. Ashcroft 
THEATER TELEVISION 
Add 

Richard Hodgson 
W. W. Lozier 



308 




Notice to Authors and Publishers Desiring to Reprint Material 
Appearing in the Journal 

While the policy of the Society is to encourage distribution of engineering infor- 
i, it has been found necessary to establish a few simple rules regarding 

>rinting of material published in the JOURNAL. All papers submitted to and 
accepted by the Society become Society property and when published in the 
JOURNAL are subject to the copyright laws of the United States of America, and 
the International and Pan-American Copyright Conventions. Permission to 
republish material from the JOURNAL must be obtained in writing from the 
General Office of the Society. Such permission ordinarily is granted upon receipt 
of approval by the author. The Society makes no charge for permission to re- 
print JOURNAL material but requires that credit be given to the JOURNAL, pref- 
erably by reference to the original publication date. However, if the material 
consists only of illustrations, a blanket credit in the preface or introduction may 
be sufficient. 

When the material originally copyrighted by another organization is printed 
in the JOURNAL by permission of the copyright holder, the Society of Motion 
Picture Engineers does not have authority to grant permission to a third party for 
further reprinting. The third party should obtain permission from the original 
copyright holder. For example, approved American Standards are copyrighted 
by the American Standards Association and reprinted in the JOURNAL by per- 
mission of the ASA. However, the SMPE does not, have authority to give a 
third party the right to reprint American Standards. This also applies to 
Proposed American Standards when the proposed changes to a previously copy- 
righted standard are minor or editorial even if the proposed changes have not 
been approved by the ASA. 

C. R. KEITH 
Editorial Vice-President 



SMPE Officers and Committees 

The names of Society Officers and of 
Committee Chairmen and Members are 
published annually in the April issue of the 
JOURNAL. Changes and corrections to these 
listings are published in the September 
JOURNAL. 



309 



Section Meetings 



Atlantic Coast 

On June 28, 1949, the Atlantic Coast Section of the Society presented "A 
Study in Television Lighting." 

This was the largest and most ambitious Eastern Section program ever held. 
Over 500 people watched the demonstration on direct-view monitors at the same 
time the action took place on the stage of the Adelphi Theater. In addition, the 
complete program was viewed by the Chicago Section through coaxial-cable 
facilities, and the general television audience in Baltimore, Washington, and 
Detroit saw the demonstration as an air show from their local DuMont stations. 

A special film section was produced by the Gray O'Reilly Studios to demon- 
strate present knowledge of the rights and wrongs of film production for television. 
Walter Kiernan served as master of ceremonies, and with Mr. O'Reilly told the 
audience exactly how the film was made and why certain lighting techniques pro- 
duce better television pictures. 

Richard Blount of the General Electric Company demonstrated on the stage 
of the theater the known rights and wrongs of television studio lighting, using the 
same talent as the film section so that the audience could see why some people 
are more difficult to light than others. 

Representative samples of poor and good lighting on original studio programs 
recorded on film via video recording techniques were viewed by the audience. 

Central 

The June 28, 1949, Central Section meeting was held in joint session with the 
Atlantic Coast Section via television and resulted in a large-screen television 
demonstration for many in the Chicago and midwest areas. 

The program, "A Study in Television Lighting," as televised is covered by the 
report of the Atlantic Coast Section. Total attendance at this meeting was 
around 500 and many were turned away at 7:00 when all the house lights were 
turned out to view the television screen. 

Following the one-hour demonstration from New York, A. H. Brolly of Tele- 
vision Associates gave a paper, "Television Studio Lighting." This paper was 
presented before the Society at the 65th Semiannual Convention in New York. 



Toledo Regional Meeting 

On June 10, 1949, an all-day Central Section Regional meeting was held in 
Toledo, Ohio. The first feature of this meeting was an inspection trip through the 
Strong Electric Corporation. After the tour, R. T. Van Niman, chairman of the 
Central Section, presided over the first technical session. Lloyd Thompson, of 
the Calvin Company, reported on the 65th Semiannual Convention and reviewed 
some of the papers presented at that time. 

A. J. Hatch, Jr., vice-president in charge of engineering of the Strong Electric 
Corporation, presented the first paper, "A Portable Device for Measuring Radiant 

310 



SECTION MEETING 311 

Energy at the Projection Aperture." The instrument described permits a value 
of total center aperture energy to be read directly from an indicating meter. 

The next paper, "The Future of Drive-in Theaters," by Charles R. Underbill, 
Jr., Product Sales Manager, Theater Equipment Sales, RCA Victor Division, 
was read by J. D. Phyfe. The construction of drive-in theaters from about eight a 
year before the war to about two hundred and fifty a year since the war has been 
largely due to the development of the in-car speaker. 

"University Productions in 16-Mm" by Robert W. Wagner, Department of 
Photography, Ohio State University, was presented by R. E. Buchanan, a director 
cameraman in this group. A production crew of four, using professional re- 
corders and cameras, is producing one picture a month. 

"A New Portable High-Intensity Arc Spotlight," was presented by Russell 
Ayling of the Strong Electric Corporation. The "Trouper" a new 215-pound 
spotlight features an automatic carbon feed and produces a clear-cut spot which 
may be varied in size. A two-element variable-focal-length lens system which 
continuously focuses on the aperture is used to project the desired spot sizes. 
Individual color filters are held in place by a permanent magnet located at the 
top of the holder. 

"A Precision Lens Testing and Copying Camera," by M. W. LaRue, Jr., of 
Bell and Howell, was well illustrated with excellent slides. A special back has 
been designed to hold the photographic material in very exact alignment and a 
special means of focusing was also described. 

The meeting was then turned over to R. T. Van Niman who acted as moderator 
for a "Symposium on Visible Music," the report of which is given below. 

At 8:00 P.M. an evening technical session was held at the Macomber Vocational 
High School. The session started with the projection of a 16-mm Technicolor 
print, "Carbon-Arc Projection," a film produced by the National Carbon Com- 
pany. Introductory comments were made by C. E. Heppberger of that company. 

"The 4-Mm Film: Its Evolution and Future" by B. A. Aughinbaugh of the 
Ohio State Department of Education, makes a plea for the use of 4-mm film in 
some type of personal viewer that could be used for communication and educa- 
tion on a par with the printed book. 

Visible Music Symposium 

Section chairman Van Niman, acting as moderator, briefly outlined the general 
subject of visible music, citing the work of Ralph Potter of Bell Telephone Labora- 
tories, Norman McLaren of the National Film Board of Canada, Robert E. Lewis 
of Armour Research Foundation, Cecil Stokes of the Crosby Research Foundation, 
and mentioned that some of the sequences in Walt Disney's "Fantasia" came close 
to what is now being considered as falling into this classification. 

The first item was a showing of several sections of one of the "Auroratone" 
films made by Cecil Stokes for the Crosby Research Foundation, and lent for the 
occasion by Mr. Crosby. These films, which are being used extensively in mental 
therapy to produce relaxation, consist of symphonic or vocal music recordings 
accompanied by slowly changing color patterns on the screen, more or less keyed 
to the mood of the music. According to the information furnished with the 
film, the abstract patterns are etched on glass plates and the color is produced 
optically, probably by a polarization process as light is projected through the 



312 SECTION MEETINGS 

moving plates into the camera. The films shown also included foreground 
patterns indicative of the subject of the musical selection. 

In discussion following this showing, Mr. Lewis pointed out that while such 
films undoubtedly have a place in the general field of visible music, the lack of 
close correlation between visual and audible stimuli and the unvarying tempo of 
the changing color patterns makes them come somewhat short of realizing the 
full capabilities of the art. 

The next items on the symposium were Norman McLaren's two short films. 
"Dots" and "Loops." These were made in the manner outlined in the March, 
1948, JOURNAL paper, "Synthetic Sound on Film," by McLaren and Lewis, and 
both the picture and the sound track were hand-drawn on 35-mm blank leader. 
The pictures, as the titles imply, are simple geometrical designs which change in 
form, color, and location in time with the sounds produced. 

In the discussion following the showing Mr. McLaren stated that the films 
have no purpose other than entertainment and relaxation, and that the principal 
value of the technique lies in the resulting close connection between the artist 
and the end result of his work because of the elimination of camera and recording 
equipment. Furthermore, sound effects not present in nature can be produced, 
and they can be closely correlated with the visual effect? for greatest dramatic 
impact. 

The next feature on the symposium was the United States premiere of Mr. 
McLaren's latest visible music film, "Be Gone Dull Care." The music for this 
film is not synthetic but is instead a special recording of a piano, drum, and double- 
bass trio playing selections varying from waltz to boogie. The visuals, however, 
are strictly abstract color, line pattern, shape, and texture animated to the music. 

Extensive discussion followed the showing and Mr. McLaren answered nu- 
merous questions regarding the technique, processing, and general philosophy of his 
version of visible music. The latter formed a natural introduction to Mr. Potter's 
portion of the symposium, which he gave under the title, "Abstract Visuals with 
Music." He pointed out that music is purely an abstract type of art and that if 
it can be combined with equally abstract forms in an attractive manner, something 
of fundamental importance in tomorrow's screen and sound entertainment has 
been created. Such abstract art forms may be used over and over without losing 
their appeal. 

Mr. Potter stated that one of the few things powerful enough to make music 
and abstract visual displays belong together is movement, and that so far as in- 
formation to the brain is concerned, sounds move just as definitely as visible 
things do. A pitch change is like visible movement across the field of view, and 
loudness changes correspond to visible movement toward and away from the 
observer. This basic concept has been employed in the sound spectroscope now 
being employed for speech studies; it shows on the scope screen an instantaneous 
picture of the various frequency components in complex sounds, with frequency 
on the horizontal axis and component intensity indicated by the vertical displace- 
ment. The picture and the sound, if it is of a musical nature, are visible music 
and are generally considered an acceptable combination, even though the picture 
is completely inartistic and only two-dimensional, because they inherently belong 
together. 



Meetings of Other Societies 



September 
Illuminating Engineering Society 

National Technical Conference 
bional Electronics Conference 

>ber 

lotographic Society of America 
Convention 

>tical Society of America 
Annual Meeting 
>ctober-November 
Radio Fall Meeting 
Joint IRE-RMA 
March, 1950 
Institute of Radio Engineers 

National Convention 
Optical Society of America 

Winter Meeting 
April, 1950 
Armed Forces 

Communications Association 
Annual Meeting 



September 19 through September 23 
French Lick, Indiana 
September 26 through September 28 
Chicago, Illinois 

October 19 through October 22 
St. Louis, Missouri 
October 27 through October 29 
Buffalo, New York 

October 31 through November 1 
Syracuse, New York 

March 6 through March 9 
New York, New York 
March 9 through March 11 
New York, New York 

April 26 through April 28 



Armed Forces Communications Association 

Society members, who are also members of the Armed Forces Communications 
Association, or who served with the military photographic services, will be in- 
terested in this report of recent AFCA activities. The first change of Association 
leadership took place July 1 when Western Electric Vice-President Frederick R. 
Lack, succeeded RCA President David Sarnoff as the President of the AFCA. 

The Third Annual National Convention of the Association was held at Wash- 
ington, D. C., March 28-29, 1949, where visiting members and officers were the 
guests of the Navy. The Signal Corps had previously served as host for the First 
Annual Meeting, while the second such meeting was under the auspices of the Air 
Force. Nearly 500 members were on hand in Washington to take part in numer- 
ous discussions and to view the many displays which the Navy had prepared. 
Ships, naval communications, and photographic equipment were featured, and 
those who attended reported that a fine time was had by all. 

The next Annual Meeting is scheduled for April 26-28, 1950, and will be held in 
New York City and Fort Monmouth, New Jersey. 

313 



Meetings af Other Societies 



TESMA Trade Show 

The Theater Equipment and Supply Manufacturers Association extends to the 
members of the Society of Motion Picture Engineers a cordial invitation to at- 
tend the Annual TESMA Trade Show and Convention to be held at the Stevens 
Hotel in Chicago, Illinois, September 26-28, 1949. On Wednesday, September 
28, in the Grand Ballroom of the Stevens Hotel, there will be a demonstration of 
the latest in large-screen theater television. Technical addresses, many of which 
will be of interest to SMPE members, will be delivered during this meeting. 



Current Literature 



THE EDITORS present for convenient reference a list of articles dealing with 
subjects cognate to motion picture engineering published in a number of 
selected journals. Photostatic or microfilm copies of articles in magazines that 
are available may be obtained from The Library of Congress, Washington, D. C., 
or from the New York Public Library, New York, N. Y., at prevailing rates. 



American Cinematographer 

30, 5, May, 1949 
Calibration of Photographic Lens 

Markings (p. 163) 
High-Speed Cineradiography (p. 164) 

H. M. GROOMS 

Photographing the 16-mm Commer- 
cial Film (p. 168) C. LORING 
Endurance Test (p. 172) J. G. ROARK 
American Photography 

43, 7, July, 1949 
Testing Shutters by Television (p. 

408) B. B. BAUER 
Electronics 

22, 6, June, 1949 
Minimizing Television Interference 

(p. 70) P. S. RAND 
International Projectionist 
24, 5, May, 1949 
TV Film Projectors (p. 9) G. W. 

TUNNELL 

Psychological Elements in Projection 

(p. 14) R. A. MITCHELL 
314 



Audio Engineering 

33, 6, June, 1949 

Magnetic Tape and Head Alignment 
Nomenclature (p. 22) ^ N. M. 
HAYNES 

33, 7, July, 1949 

Auditory Component Control for the 
Legitimate Theatre (p. 15) J. H. 
BEAUMONT 

Importance of Groove Fit in Lateral 
Recordings (p. 18) D. R. ANDREWS 

Photographic Age 

4, 5, May, 1949 

Telephoned Television Has Indus- 
trial Future. The Story of Rem- 
ington Rand's Lightweight Video 
Camera (p. 17) 

Radio and Television News 

41, 6, June, 1949 

A Three-Dimensional Reproducer 
System (p. 44) M. WOLFE 



Book Reviews 



Elements of Sound Recording, by John G. Frayne and 
Halley Wolfe 

Published (1949) by John Wiley and Sons, 440 Fourth Avenue, New York 16, 
N. Y. 674 pages + 12-page index + vii pages. 463 illustrations. &/ 4 X $ 1 /* 
inches. Price, $8.50. 

Here at last is a book, for both the student and experienced recording engineer, 
that contains a wealth of up-to-date, useful information in a field which is so 
specialized as most everything is nowadays that very little outside of the 
professional journals is available in book form. The authors are well qualified to 
prepare such a volume, and have succeeded in presenting under one cover much 
of the meat of the subject. Diagrams and illustrations are profusely employed to 
supplement the text. Mathematical analyses are sparingly used and then only 
to illustrate basic principles. 

Briefly to orient the newcomer to the field, the first few chapters deal with the 
nature of sound, sound waves, electrical, acoustical, and mechanical circuits. 
Chapter III, and the several following, cover microphones and their uses, vacuum 
tubes, audio amplifiers, network theory, filters, and equalizers. And here it is 
well to add that there are many charts and tables which are useful in determining 
constants for mixer circuits, loss pads, and filters. 

Chapter X begins the discussion of practices largely unique in recording: 
compression and limiting, recording systems, disk recording, disk records and 
their processing. There follows, in considerable detail, subject matter on variable- 
density and variable-area film recording. Noise-reduction methods are thor- 
oughly described. 

The chapter on film laboratory processes contains much information on modern 
laboratory processing methods for sound film. A chapter is included on 
recording techniques. Film reproducing systems, both 35-mm and 16-mm, are 
described with much helpful information on theater sound systems and how to 
obtain the best quality from 16-mm sound films. 

Of timely interest in the present state of the recording art is a chapter on mag- 
netic recording its basic principles, types of systems, and professional uses. 
There are chapters on loudspeaker systems and acoustics of stages and theaters. 
The final subject looks to the future with a review of stereophonic recording and 
reproduction relating the work done to the present time. Systems are described 
and results discussed, together with the operating problems which were en- 
countered. 

The subject of sound recording has so many ramifications that it is difficult to 
cover all parts adequately. This fact is recognized by the authors, who include 
a number of pertinent references at the end of each chapter to enable the reader 
to go into many of the subjects at greater length. For a thorough grounding in 
sound recording and reproduction, this book is a worth-while addition to the refer- 
ence library of the engineer in this field. 

LLOYD T. GOLDSMITH 

Warner Brothers Pictures 

Burbank, Calif. 

315 



Book Reviews 



Magnetic Recording, by S. J. Begun 

Published (1949) by Murray Hill Books, Inc., 232 Madison Avenue, New York 
16, N. Y. Q 1 /* X 9 X A inches. 223 pages + 7-page glossary + 8-page index + 
x pages. 146 illustrations. Price, $5.00. 

"Magnetic Recording" is devoted almost entirely to a discussion of magnetic 
recording, both in its theoretical aspects and practical applications. The book is 
very timely and will be of great value to those interested in understanding the 
nature of the magnetic-recording process as well as to those who are interested in 
the more practical side of designing equipment for various commercial usages. 
The chapter on the theory of magnetic recording is extremely well written and 
explains in considerable detail the influence of the various parameters entering 
into magnetic recording. The discussion of the effect of the direct-current and 
alternating-current bias is very thorough, and in the case of the alternating- 
current bias represents, in the reviewer's opinion, one of the most lucid explana- 
tions yet offered. The chapter devoted to components of the magnetic-recording 
system gives a very detailed discussion of the various recording media that have 
been used to date in magnetic recording. In this chapter, and also in the next one 
on magnetic-recording equipment, undue emphasis may seem to have been placed 
on wire-recording systems. This apparent misplacement of emphasis, however, 
can very well be attributed to the necessary hiatus between the writing of the 
book and its publication. The very rapid adoption of the powdered iron-oxide 
coated tape in the last few years has, of course, recently tended to obsolete wire 
and steel-tape recorders, at least for professional applications. 

The book is well illustrated and a very complete description, with appropriate 
photographs, is given of the various types of commercial recorders that had 
appeared on the market up to the time of preparation of the manuscript. 

The chapter entitled "Applications of Magnetic Recording" describes applica- 
tions to artificial-reverberation devices, speech-scrambling, recording of transients, 
applications to telegraphy and telephony, transcription recording, and motion 
pictures. The treatment of the last item is quite brief and is undoubtedly neces- 
sarily so because of the rather belated interest of the motion picture industry in 
the magnetic-recording method. 

JOHN G. FRAYNE 
Western Electric Company 
Hollywood 38, Calif. 
+ 

EMPLOYMENT SERVICE 
POSITION WANTED 

16-MM PRODUCTION SPECIALIST: Twelve years' experience 
in all phases of 16-mm production and distribution including 
camera, sound recording, editing, animation, and public relations. 
Seven years' experience in administration and supervision of pro- 
duction unit. Presently employed. Age 35 years. Desires posi- 
tion in television, educational, or industrial field inaugurating a 
motion picture program. Write Alfred Y. Lytle, 15 Sutton Road, 
Rocky Hill, Connecticut. 

316 



New Products 



Further information concerning the material described below can 
be obtained by writing direct to the manufacturers. As in the case 
of technical papers, publication of these news items does not consti- 
tute endorsement of the manufacturer's statements nor of his products. 



)p Watch and Timer 

Moss and Robinson, 8 W. 47 St., 
[ew York 19, N. Y., have designed a 
watch and timer especially for the 
)tion picture industry. This watch 
)les the user instantly to ascertain 
either simultaneously or individually 
the amount of film footage needed in 
16- or 35-mm film on a precheck or re- 
hearsal of dialog or narration. 




The dial has three scales as follows: 
Red scale divides the minute into 90 
parts, synchronizing with 35-mm film 
(90 feet per minute). Blue scale di- 
vides the minute into 60 seconds. 
Black scale divides the minute into 36 
parts, synchronizing with 16-mm film 
(36 feet per minute). 

The watch can be used by script 
writers, directors, and in the editing 
room. The dial also serves as an 
immediate reduction table from 35 to 
16 mm. 



Two models are offered. The illus- 
tration shown is l x /4 inches in diameter 
and is regulation pocket size. The 
second model is 2 x /4 inches in diameter 
for those who find a larger size watch 
more to their liking. 



100- Watt Class A Amplifier 

A new 100-watt Class A amplifier 
built as a single unit has been designed 
by the Westrex Corporation, 195 
Broadway, New York 7, N. Y. It is 
said to be the first amplifier of its kind 
available for theater use. 

The Class A push-pull power stage 
reduces harmonic distortion to less than 




317 



New Products 



TTurther information concerning the material described below can 
JL be obtained by writing direct to the manufacturers. As in the case 
of technical papers, publication of these news items does not consti- 
tute endorsement of the manufacturer's statements nor of his products. 



one and one-half per cent at the full 
rated output. Microswitches auto- 
matically provide full protection 
against high-voltage hazards. 

The voltage driver unit is identical 
to that used in all Westrex high- 
powered amplifiers and may be com- 
pletely replaced, in the event of failure, 
simply by the use of a screw driver. 
Only one electrolytic capacitor is used 
in amplification, that being of the plug- 
in type. All resistors, except those in 
the power stages, are of a precision type 
with a maximum permissible tolerance 
of one per cent. 

Mounted in an attractive floor-type 
cabinet, this 100-watt system permits 
maximum flexibility in the arrange- 
ment of components to meet individual 
theater requirements. Full-length 
double doors at the rear provide easy 
access, while spare tubes and plug-in 
capacitors are stored within the cabinet 
in easy reach. 



New Theater Amplifier System 

Westrex also announces a new line 
of theater amplifier systems which 
provides standard relay-rack panels in 
a floor-mounted cabinet for all but the 
smallest system. As an aid to servicing 
the deep amplifier chassis a door switch 
automatically turns on a light inside 
the chassis when the front mat is re- 
moved. A standard voltage amplifier, 
which may be mounted 011 a 15-, 40-, 
50-, or 100-watt amplifier chassis, is 
connected by means of small metal 
straps so that it may be disconnected 
318 



and replaced with only a screw driver. 
Normal space currents are indicated at 
11 points in the system by means of a 
"100 per cent" meter. 

Another feature is a small plug-in 
phototube amplifier, as shown in the 
photograph. Change-over between 



. 




machines is effected by interlocking 
relays operated by a push button 
which may be placed at any convenient 
location. When stand-by amplifiers 
are provided, they may be put in use 
by means of a single switch which 
simultaneously cuts over amplifiers, 
rectifiers, and horns. Accessories such 
as mixing panels and nonsynchronous 
reproducer amplifier-equalizers are also 
available. 



Journal of the 

Society of Motion Picture Engineers 

VOLUME 53 OCTOBER 1949 NUMBER 4 

PAGE 

Theater Television Today 

JOHN EVANS McCoy AND HARRY P. WARNER 321 

FCC Allocation of Frequencies for Theater Television 351 

Statement on Theater Television 354 

Portable Device for Measuring Radiant Energy at the 

Projector Aperture A. J. HATCH, JR. 363 

Report of Lens-Calibration Subcommittee 368 

Precision Lens-Testing and Copying Camera. . .M. W. LA RUE 379 
35-Mm and 16-Mm Sound-on-Film Reproducing Characteristic 

JOHN K. HILLIARD 389 

Desirable Locations for Theater Sites E.G. FALUDI 396 

New Portable High-Intensity Arc Spotlight 

RUSSELL J. AYLING 408 

SMPE Awards 417 

Book Reviews : 

"Electron Tubes" (Volumes I and II), Published by RCA 
Review 

Reviewed by L. F. Brown 422 

"The Sound Track Book of the Theatre," Published by The 
Sound Track 

Reviewed by William K. Aughenbaugh 422 

Current Literature 424 

To the Editor ' 425 

European Advisory Committee 425 

New Products 426 

ARTHUR C. DOWNES HELEN M. STOTE NORWOOD L. SIMMONS 

Chairman Editor Chairman 

Board of Editors Papers Committee 

Subscription to nonmembers, $12.50 per annum; to members, $6.25 per annum, included in 
their annual membership dues; single copies, $1.50. Order from the Society's General Office. 
A discount of ten per cent is allowed to accredited agencies on orders for subscriptions and 
single copies. Published monthly at Easton, Pa., by the Society of Motion Picture Engineers, 
Inc. Publication Office, 20th & Northampton Sts., Easton, Pa. General and Editorial Office, 
342 Madison Ave., New York 17, N. Y. Entered as second-class matter January 15, 1930, 
at the Post Office at Easton, Pa., under the Act of March 3, 1879. 

Copyright, 1949, by the Society of Motion Picture Engineers, Inc. Permission to republish 
material from the JOURNAL must be obtained in writing from the General Office of the Society. 
Copyright under International Copyright Convention and Pan-American Convention. The 
Society is not responsible for statements of authors or contributors. 



Society of 

Motion Picture Engineers 

342 MADISON AVENUE NEW YORK 17, N. Y. TEL. Mu 2-2185 
BOYCE NEMEC . . . EXECUTIVE SECRETARY 

OFFICERS 

1949-1950 



PRESIDENT 
Earl I. Sponable 
460 W. 54 St. 
New York 19, N. Y. 

EXECUTIVE 
VICE-PRESIDENT 
Peter Mole 

941 N. Sycamore Ave. 
Hollywood 38, Calif. 



PAST-PRESIDENT 
Loren L. Ryder 
5451 Marathon St. 
Hollywood 38, Calif. 

EDITORIAL 
VICE-PRESIDENT 
Clyde R. Keith 
120 Broadway 
New York 5, N. Y. 



1948-1949 



ENGINEERING 
VICE-PRESIDENT 
John A. Maurer 
37-0131 St. 
Long Island City 1, N. Y. 



TREASURER 
Ralph B. Austrian 
25 W. 54 St. 
New York 19, N. Y. 



SECRETARY 
Robert M. Corbin 
343 State St. 
Rochester 4, N. Y. 

CONVENTION 
VICE-PRESIDENT 
William C. Kunzmann 
Box 6087 
Cleveland 1, Ohio 

1949 

FINANCIAL 
VICE-PRESIDENT 
David B. Joy 
30 E. 42 St. 
New York 17, N. Y. 



1948-1949 

Alan W. Cook 
4 Druid PI. 
Binghamton, N. Y. 



Lloyd T. Goldsmith 
Warner Brothers 
Burbank, Calif. 



Paul J. Larsen 
508 S. Tulane St. 
Albuquerque, N. M. 



Gordon E. Sawyer 
857 N. Martel Ave. 
Hollywood 46, Calif. 



Governors 
1949 

James Frank, Jr. 
1310 Peachtree Battle 

Ave., N. W. 
Atlanta, Ga. 

William B. Lodge 
485 Madison Ave. 
New York 22, N. Y. 

William H. Rivers 
342 Madison Ave. 
New York 17, N. Y. 

Sidney P. Solow 
959 Seward St. 
Hollywood 38, Calif. 

R. T. Van Niman 
4431 W. Lake St. 
Chicago 24, 111. 



1949-1950 

Herbert Barnett 
Manville Lane 
Pleasantville, N. Y. 



Fred T. Bowditch 
Box 6087 
Cleveland 1, Ohio 



Kenneth F. Morgan 
6601 Romaine St. 
Los Angeles 38, Calif. 



Norwood L. Simmons 
6706 Santa Monica Blvd. 
Hollywood 38, Calif. 






Theater Television Today 



BY JOHN EVANS McCOYf 

FEDERAL COMMUNICATIONS COMMISSION, WASHINGTON, D. C. 

AND 

HARRY P. WARNER f 

SEGAL, SMITH, AND HENNESSEY, WASHINGTON, D. C. 

Summary An historical review of theater television's growth from 1930 
to 1949 is presented. The authors outline the status of theater television 
equipment used for direct or "film storage" projection, including an analy- 
sis of the radio-frequency requirements, methods of program distribution, 
and capital costs of a nation-wide theater television system. Some aspects 
of theater television programming are also presented. 

I. INTRODUCTION 

PHERE ARE STRONG signs that the motion picture industry, in 
L facing the problems created by the spectacular boom in home 
television and its impact on motion picture attendance, intends to 
"fight television with television." Primarily this means that large- 
screen theater television may soon be brought out of the laboratory 
and private-demonstration stage and revealed full-blown to the 
motion picture going public. 1 The creation of what amounts to a new 
medium of mass entertainment and communication involves numerous 
technical, economic, and legal problems, and calls for broad vision, 
clarity of thinking, and inspired leadership. The purpose of this 
article is to discuss the principal problems in the light of present 
knowledge in an endeavor to contribute to a wider understanding by 
the motion picture and television industry of the nature and scope of 
these problems. 

Theater television involves the exhibition of visual and aural tele- 
vision programs on large screens (about 15 by 20 feet), in motion 

* Reprinted from Vol. IV, No. 2, of The Hollywood Quarterly with its kind 
permission. 

t NOTE: The opinions and conclusions stated are the personal views of the 
authors. John Evans McCoy is Chief, Television Branch, Law Bureau, Federal 
Communications Commission; Harry P. Warner is author of "Radio and Televi- 
sion Law," contributor to law journals and other periodicals on communications 
law, and is associated with Segal, Smith, and Hennessey. 

OCTOBER, 1949 JOURNAL OF THE SMPE VOLUME 53 321 



322 McCoY AND WARNER October 

picture theaters. These programs are photographed outside the 
theater by regular television cameras; transmitted to the exhibiting 
theater by television techniques over microwave radio relays, coaxial 
cables, or telephone wires; and received in the exhibiting theater by 
television receiving equipment. In the United States, two systems of 
theater television equipment have been developed for installation in 
the exhibiting theater for the purpose of projecting the television pro- 
gram as received in the theater to the screen: the direct-projection 
system and the intermediate-film system. 

At the outset, theater television must be distinguished from tele- 
vision broadcasting or "home television." A television broadcast 
station, as contemplated by the Communications Act and as denned 
by the rules of the Federal Communications Commission, means, "a 
broadcast station utilizing both television and telephony to provide 
combination and simultaneous visual and aural programs intended to 
be received directly by the general public" In other words, television 
broadcast stations licensed by the FCC are intended to transmit tele- 
vision programs to the public generally, primarily for reception in the 
home. Theater television does not come within this definition be- 
cause its programs are beamed directly by means of closed-circuit 
coaxial cables or wires or by directional microwave relays to the 
exhibiting theater, and they are not intended to be received by the 
general public. 

II. THEATER TELEVISION HISTORY 

Large-screen projection television is nearly as old as the direct-view 
television that predominates in home television reception. In the year 
1930, only two years after the Federal Radio Commission authorized 
the first experimental television broadcast stations, television on a 6- 
by 8-foot screen was shown by the Radio Corporation of America at 
RKO-Proctor's 58th Street Theater in New York City. Large-screen 
theater television on 15- by 18-foot screens was exhibited in London, 
England, in 1939, and by the end of that year five theaters were 
equipped for theater television. In 1941, a Madison Square Garden 
prize fight and a Brooklyn Dodgers baseball -game were demon- 
strated to the public .on a 15- by 20-foot screen in the New Yorker 
Theater by RCA. The onset of the war interrupted the further de- 
velopment and the commercialization of theater television both in 
England and in the United States. 

During the general frequency allocation hearings held before the 



1949 THEATER TELEVISION 323 

FCC in 1944 and 1945, Paul J. Larsen on behalf of the Society of 
Motion Picture Engineers appeared before the FCC and requested the 
allocation of frequencies to theater television. 

At the termination of hostilities, Paramount Pictures, Inc., under 
the direction of Paul Raibourn, directed its research to the develop- 
ment of the intermediate-film method of theater television, which 
culminated on April 14, 1948, in the surprise public exhibition of a 15- 
minute televised newsreel at the Paramount Theater in New York. 
The television pictures were transmitted via a 7000-megacycle micro- 
wave relay from the Navy YMCA, Brooklyn, to the top of the Daily 
News Building on East 42 Street, thence to the Paramount Build- 
ing at Broadway and 43 Street, and from there down a coaxial cable 
to the receiving and film-making equipment. The pictures were 
filmed on regular 35-mm film and, because of the new rapid film-de- 
veloping process, reached the 18- by 24-foot screen 66 seconds after 
the scenes were shot. On June 25, 1948, the same process was em- 
ployed in a showing of the Louis-Walcott prize fight on the screen of 
the Paramount Theater, and since that date similar exhibitions have 
been held in the Paramount Theater on an almost weekly basis. 

Meanwhile, RCA Laboratories, Inc., collaborating with 20th Cen- 
tury-Fox Film Corporation and Warner Brothers Pictures, Inc., pro- 
ceeded with the development of the direct-projection system of 
theater television. In July, 1947, Earl I. Sponable, technical director 
of 20th Century-Fox, and Colonel Nathan Levinson of Warner 
Brothers, signed research and development agreements with RCA for 
I joint participation in the development of this system. The three 
I organizations sponsored a private showing of theater-size television 
(15- by 20-foot), at Warner's Burbank Studio in May, 1948, during 
I the National Association of Broadcasters' Convention, and on June 
I 25, 1948, history was made by the public showing in the Fox-Phila- 
delphia Theater of instantaneous television pictures of the Louis- 
Walcott prize fight using an intercity relay from New York to 
Philadelphia. The program was picked up at the Yankee Stadium 
New York, and relayed by microwave relays successively to WNBT, 
Empire State Building, New York City, WPTZ, Wyndmoor, Penn- 
I sylvania, and the Fox-Philadelphia Theater, a total distance of about 
100 miles. From the roof of the theater the program was run to the 
1 receiving and projecting equipment by coaxial cable. The reactions 
, of the audience in the 2400-seat theater were described as highly en- 
j thusiastic. Recently, on April 4, 1949, the RCA-Fox-Warner system 



324 McCoy AND WARNER October 

was demonstrated at the Convention of the Society of Motion Picture 
Engineers at the Statler Hotel, New York, the programs being relayed 
in part via balanced telephone wires, furnished by the telephone com- 
pany, from the Empire State Building to the hotel. The RCA-Fox- 
Warner group has also developed intermediate-film equipment. 

III. THEATER EQUIPMENT REQUIRED 

The equipment required for theater television falls into two general! 
categories, the equipment installed in the theater for receiving the pro^ 
gram and projecting it to the screen, and the equipment used outA 
side the theater for pickup of programs and relay to the theater. 

The first problem undertaken by the engineers in developing theatei 
television was the development of equipment for installation in the 
theater. This equipment has now reached the point where two sys- 
tems of equipment are reported to be substantially ready for com- 
mercial use: the direct- (or instantaneous-projection} system, anc 
the intermediate-film (or film-storage) system." 2 

The direct-projection system, developed in the United States by the 
RCA-Fox- Warner group, consists of (1) the receiver-projector, which 
includes a projection cathode-ray tube as the source of the light 
image, and the optical system which projects the image to the screer 
by a reflective process ; (2) a viewing screen ; (3) a television contro 
console; and (4) a power-supply rack and high-voltage power unit. 3 I] 
the television program is brought to the theater by a microwave relaj; 
system, the theater installation will also include a receiving antenna 
receiver, and a transmission line to carry the program from the an- 
tenna to the receiver. 

RCA's new projector, demonstrated to the SMPE Convention on 
April 4, 1949, utilizes a 12-inch cathode-ray picture tube inclosed in a 
barrel about the size and appearance of a Bendix home washind 
machine. The optical system enclosed in the same barrel employs a 
21-inch spherical mirror and a correcting lens, employing the Schmidtj| 
type optical system. As installed, the picture tube faces the rear oi 
the theater and projects the picture on the spherical mirror which reli 
fleets it toward the screen. The picture passes through the correcting 
lens on its way to the screen. The picture tube operates with 80,00(( 
volts as compared to the 9000 volts used in most home television rd 
ceivers. The optical system is capable of projecting a screen image IS 
by 24 feet, which is larger than the average motion picture screen! 
The entire projector unit weighs about 180 pounds and is designed foij 



1& 



1949 THEATER TELEVISION 325 

installation either suspended from the balcony or mounted on a plat- 
form in front of the theater mezzanine rather than in the regular pro- 
jection booth. The ' 'throw distance" can be varied from 45 to 80 feet. 
RCA plans to manufacture pilot models before the end of 1949 for sale 
to theaters at a price under $25,000. The first such unit has been 
ordered for installation in the Fabian Fox Theater in Brooklyn, 
New York. The installation of microwave receiving equipment and 
a transmission line would cost approximately $3500 at present prices. 
The viewing screen is an important element of the direct-projection 
system. The cathode-ray tube, which is the light source for projection 
television at this stage of development cannot compete with the car- 
bon arc which is the light source in conventional motion picture pro- 
jectors. Thus, while standard motion picture screens are generally 
Jnot directional in distributing the light, much research has been de- 
1 voted to the development of directional screens for theater 
i television. 

The Paramount intermediate-film system consists of (1) television 
\ receiving equipment , (2) a specially developed recording camera, (3) 
I rapid film-processing equipment, capable of developing film in less 
'than a minute, and (4) a conventional 35-mm motion picture projec- 
! tor. If the program is received over microwave relay, receiving equip- 
jrnent and a transmission line must be installed. 

The television receiving equipment is contained in one unit, which 
c douses both video and audio equipment, and high- and low-voltage 
I power supplies. 

The receiver utilizes a 10-inch cathode-ray tube, aluminum-backed, 
ind with a flat-face screen, from which the picture is photographed. 
lA 15-inch cathode-ray tube is provided for monitoring purposes. 
The special recording camera utilizes an electronic shutter, rather 
;han a mechanical one, and is synchronized at the standard film rate 
}f 24 frames per second. Twenty frames before exposure of the pic- 
ture the sound track is impressed on the film. One of the amazing 
Matures of this system is the high-speed film-processing unit, into 
ivhich the film passes by chute directly from the recording camera. 
The film is lead by vertical chutes into solutions which develop, fix, 
xnd wash it, and into a compartment which dries it in a maximum 
Deriod of 66 seconds. The processed film either may be wound on 
'I "eels or fed directly to the conventional 35-mm film projector by chute. 
The equipment requires a room of about 10 by 20 feet floor space, 
vhieh is usually located directly above the projection booth. Jit has 



326 McCoy AND WARNER October 

been reliably, and probably conservatively, stated that the cost of the 
receiver, camera, and processing unit will be approximately $35,000 
plus installation. Units of this type have been installed in Para- 
mount theaters in New York, Chicago, and Los Angeles. It is likely 
that the price of the three units may be in the $15,000 to $20,000 
range, plus installation, when available in commercial quantities. 
The microwave receiving equipment and transmission line would add| 
an additional $3500. 

Theater television equipment has not yet attained the perfection of 
class A motion pictures, although engineering opinion supports the 
conclusion that such perfection is attainable. However, 20th Cen- 
tury-Fox recently advised the FCC that in its opinion "the generatioi 
of a theater television picture of suitable quality is not only possible 
but practical." 4 The final arbiter of picture quality is the audience, 
and theater television has been received favorably by the public. 
There is some danger that in waiting for technical perfection, the 
motion picture industry may lose the opportunity to secure the radi< 
frequencies and other transmission facilities that would make theat< 
television possible. 

IV. DISTRIBUTION OF THEATER TELEVISION PROGRAMS 

The most critical "and urgent problems facing the proponents o\ 
theater television involve determination of methods and means f< 
transmitting television programs to the exhibiting theaters. Theat( 
television essentially is a system of distribution of programs by televisioi 
It is well known that television programs may be transmitted by radic 
relays, by coaxial cable, and by telephone wires for short distanc< 
The opportunity to use these avenues of program distribution canm 
be had merely for the asking. The use of radio relays requires aj 
proval by the Federal Communications Commission. The use 
coaxial cable and telephone wires requires the co-operation of 
American Telephone and Telegraph Company and the Bell Syst 
Wherever theater television applies for transmission facilities 
must prove a demand for the facilities and it must overcome sti 
competition for the same facilities by broadcast television networl 
and stations, and by other users of the same facilities. 

Theater television may be carried out as an independent enterpru 
by one theater which provides or obtains all of its own transmissic 
facilities, or it may be carried out as a common enterprise by sevei 



1949 THEATER TELEVISION 327 

theaters in a city sharing certain facilities and co-operating together. 
Such a co-operative theater television group is described hereafter. 
Since the capital and operating expenses of any television enterprise 
are substantial, it is assumed that some or all the theaters in a city will 
form a co-operative group, and that this organization will be predomi- 
nant in the theater television industry. The present discussion, 
therefore, is limited to a description of theater television in cities where 
it will be promoted and carried on by one or more co-operative groups. 
Theater television envisioning co-operative action by several thea- 
ters in a single city needs television transmission facilities for five 
purposes : 

1. For distribution of programs from a central distributing point 
to groups of theaters. Such facilities may be described as ' 'Multiple- 
Addressee Systems." 

2. For transmission of programs from studios and regular origina- 
tion points to the central distributing point. In broadcasting termi- 
nology, such fixed circuits are termed ''Studio-Transmitter Links." 

3. For mobile remote pickup of programs and transmission to the 
central distributing point. In broadcasting terminology, these mo- 
bile units are known as "remote pickups," and are used for the origi- 
nation of programs such as sports events, parades, news events, and 
stage shows. 

4. For transmission of programs to intercity relay points. These 
fixed circuits also may be classified as "Studio-Transmitter Links." 

5. For intercity relay of programs. 

The use of transmission facilities by co-operative theater television 
groups is most easily explained by reference to Fig. 1, which is a dia- 
gram of a typical theater television system in two imaginary cities, 
City A and City B. City A is assumed to be located on the A. T. andT. 
coaxial cable, and City B is assumed to be located off the coaxial cable 
about 35 miles east of City A. City A contains 25 motion picture 
theaters which are part of the co-operative theater television group 
Hand receive programs from it. City B contains 15 such theaters. 

In each city the key point of the theater television system is the 
[central distributing point where the multiple-addressee system is le- 
gated (marked on the diagram, "MAS"). The co-operative group in 
City A maintains studio-transmitter links (STL) from one studio or 
(theater which produces a daily stage show, and from the Municipal 
1 1 Auditorium. It also utilizes two mobile remote pickup units, which 
,are available for use in appropriate scenes of action throughout the 



328 



McCoy AND WARNER 



October! 



area. It maintains a microwave relay transmitter (M/W Relay), 
which is used to transmit programs to City B on a one-way circuit. 
In City A a studio-transmitter link (STL) connects the main distribut-l 
ing point with the intercity relay. 



CITY B 




AT&T CO-Axial 
Cable 



Fig. 1 Typical two-city theater television relay system. 



The co-operative group in City B, running a "barebones" opera tioi 
and depending on City A and the theater network for substantially al 
programs requires fewer transmission facilities. It must maintain t 
multiple-addressee system (MAS) at the central distributing point, 
microwave relay receiver (M/W Relay), and a studio-transmittei 
link (STL) to connect the two points. It requires no other t 
mission facilities. 



1949 THEATER TELEVISION 329 

V. CAPITAL COSTS 

What investment will be required to install the theater television 
systems described, in the two cities? The price of the theater in- 
stallations required in each theater has been estimated above to be 
approximately $25,000 per theater, regardless of whether the direct- 
projection or the intermediate-film system is used. The following 
discussion endeavors to fix estimated costs of the equipment required 
by the co-operative group of City A. 

1. Multiple- Addressee System The basic elements of this system 
are a television transmitter, associated control and power equipment, 
film-recording and film-camera equipment, and a multibeam, highly 
directional, antenna array. If live programs are to be produced lo- 
cally, studio video camera equipment and studios with proper lighting 
must be provided. Programs would be beamed in the necessary di- 
rections to permit reception by each of the theaters equipped to re- 
ceive the transmissions. Three such directional beams are pictured 
in Fig. 1 at City A. In the frequencies involved, a low-power video 
transmitter would provide satisfactory signals to cover the area in 
which the associated theaters were located. While no such multiple- 
addressee television system is in operation in this country, the engi- 
neering principles underlying it are not new, and there is no doubt 
that it could be designed and manufactured within a reasonably short 
period after order. With the exception of the directive antenna, the 
other equipment would be adapted readily from television broadcast 
equipment now in use. The directive antenna presents no excep- 
tionally difficult problems, although it would have to be engineered on 
a custom basis to fit the problems of the particular city involved, with 
the location of theaters in view. The capital cost of such a system, 
without studio-camera equipment and studios, is estimated at ap- 
proximately $175,000. This includes $25,000 for the acquisition of in- 
stantaneous film-recording equipment, and $50,000 as the cost of the 
directive-antenna array. With studio-camera equipment and studios, 
about $100,000 would be added to the cost. These estimates do not 
include expenditures for acquisition or remodeling of buildings or 
land. 

2. Studio-Transmitter Links The necessary facilities to connect 
studios or program origination points with the central distributing 
point would be substantially the same as the equipment used by tele- 
vision broadcast stations to link studio and transmitter. These con- 
nections may be made by microwave relay, coaxial cable, or by 






330 McCoy AND WARNER October 

balanced telephone wires over distances from one or two miles. If 
studio-transmitter radio links are deemed desirable, their cost would 
be approximately $15,000 per installation. If coaxial cable or tele- 
vision wires are used, the telephone company will provide the service 
at regular* rates, and capital costs to the theater television system will 
be nominal. 

3. Remote Pickups The two remote pickup units contemplated 
for City A would cost approximately $50,000 per unit. This includes 
two portable camera units, audio equipment, a small truck, and the 
video-link equipment. The audio link is a telephone circuit. The 
video relay may be used over distances of from 10 to 15 miles, but 
only over line-of-sight in the high frequencies used. This equipment 
may be owned and operated, or may be leased from the telephone 
company, or, perhaps, from local television broadcast stations. 

4. Intercity Relays The one-way intercity relay circuit from City 
A to City B, contemplated in Fig. 1, is estimated to cost from $25,000 
to $50,000. This figure includes both the transmitting and receiving 
units. As described above, the relay transmitter in City A and the re- 
lay receiver in City B would be connected with the central distributing 
point in each city by studio-transmitter links, costing approximately 
$15,000 each. However, given an appropriate location of the relay 
units, coaxial-cable connections might be provided by the telephone 
company. 

On the above basis, a rough estimate of the capital investment re- 
quired by the co-operative theater group in City A would total ap- 
proximately $445,000, consisting of (1) multiple-addressee system 
and associated equipment including studio equipment, $275,000, (2) 
three studio-transmitter links, $45,000, (3) two remote pickup units, 
$100,000, and (4) 50 per cent of the cost of the intercity relay in- 
stallation, $25,000. 

The capital investment required in City B would be substantially 
less. The cost of the multiple-addressee system, eliminating $100,000 
as the cost of items of studio equipment and studios that full-scale 
program production would require, would come to $175,000 or less. 
If an intermediate-film- recording unit were not used in City B, this 
cost would be reduced by another $25,000. The studio-transmitter 
link and intercity relay receiver installations would add approxi- 
mately $40,000. Thus, the total investment at City B would approxi- 
mate from $190,000 to $215,000. 



1949 THEATER TELEVISION 331 

VI. TRANSMISSION FACILITIES FOR THEATER TELEVISION 

Availability of Relay Facilities Theater television programs may be 
relayed by microwave radio relays, coaxial cables, or balanced tele- 
phone wires. The telephone company in certain areas is already 
equipped to furnish all three types of transmission facilities, and is 
furnishing these services on a rental basis to certain television broad- 
cast stations and networks. The services furnished by the telephone 
company include intercity transmission of programs by coaxial cable 
or by microwave relay; studio-transmitter links and remote pickups 
by cable, relay, or wire. Other organizations also are equipped to 
furnish intercity microwave relay service in certain areas. The 
principal problems concerning the three methods of relay will be de- 
scribed briefly. 

A. T. and T.'s Coaxial Cable By May, 1949, the A. T. and T. co- 
axial cable provided the primary means of transmission of television 
programs from New York to Richmond on the east coast (through the 
cities of Philadelphia, Baltimore, and Washington) ; from Philadelphia 
to Chicago (through the cities of Pittsburgh, Cleveland, and Toledo) ; 
from Cleveland to Buffalo; and from Chicago to St. Louis. By the 
same month, A. T. and T. also had in operation microwave radio relays 
for transmission of television programs from New York to Boston; 
Toledo to Detroit; and Chicago to Milwaukee. Before the end of 
1949, A. T. and T. plans to complete network links (either coaxial cable 
or radio relay) from Boston to Providence; New York to Syracuse 
(through Schenectady and Utica) ; Buffalo to Rochester; Milwaukee 
to Madison; Philadelphia to Wilmington; and from Toledo south to 
Dayton, Cincinnati, and Columbus. Likewise, in 1949 a radio relay 
between San Francisco and Los Angeles is planned. 

At the present time, the Bell System does not contemplate ex- 
tension of its television relay facilities across the continent in the near 
future. The means for a transcontinental television network, however, 
now exist since the coaxial cable, equipped for long-distance telephone 
service, has been completed between St. Louis and Los Angeles. 
Telephone company officials have recently stated that a television 
channel from New York to Los Angeles could be made ready in about 
a year after the service is ordered. 

The Bell System coaxial cable, first authorized by the FCC in 1936 
on an experimental basis, 5 is primarily used to multiplex telephone 
transmission. As many as 480 telephone conversations can be trans- 
mitted simultaneously on a single channel of each 8-channel cable 



332 McCoy AND WARNER October 

without mutual interference. The relay and terminal equipment in- 
stalled was originally designed for this purpose. However, it was rec- 
ognized from the first that the bandwidth of each cable channel was 
sufficient to permit television transmission. New terminal equip- 
ment must be installed to convert the cable for television transmis- 
sions. The present equipment now used on the coaxial cable for tele- 
vision transmission will permit transmission of a television band of 
2.7 megacycles. This is not sufficient to carry the full requirements of 
the present 525-line, 4.5-megacycle standard television broadcasts, but 
recent developmental work will make possible wider-band television 
transmission (up to 8 megacycles) when the demand arises. While 
current theater television has adopted the 525-line standard used by 
television broadcast stations, full utilization of the possibilities of 
theater television may require the use of higher definition and wider- 
band transmissions, which would raise a problem as to the suitability 
of the coaxial cable for intercity transmission of the theater television 
programs. If color television is desired by the theater television 
interests, bandwidths of from 8 to 16 megacycles probably would be 
desirable if not essential. At the present time, no extensive intracity 
coaxial -cable system is available, but some coaxial-cable links are in 
operation in New York and other cities. 

The current coaxial-cable television rates filed by the A. T. and T. 
and associated Bell System telephone companies and effective May 1, 
1948, contemplate charges which raise a serious economic question 
both for television broadcast stations and theater television. A single 
television channel between two cities costs the user $35.00 a month 
per airline mile for eight consecutive hours each day, and $2.00 a 
month per mile for each additional consecutive hour. Thus, for 240 
hours of service in one month, the rate would be $35.00 per airline 
mile. For occasional or part-time service, the rate is $1.00 per airline 
mile for the first hour and 25 cents per mile for each additional con- 
secutive 15 minutes. Additional charges are made for the use of 
terminal equipment; $500 per month is charged for a connection to 
the television network for eight consecutive hours daily. This inter- 
connection charge for occasional service is $200 per month, plus $10.00 
per hour of use. To complete the service, a Bell System sound channel 
must be used, at the regular rates applicable to the frequency- 
modulated service. If two users share time on the 'same channel, 
$25.00 a month per airline mile is charged for four consecutive hours of 
daily service, with an interconnection charge of $350 for each user. 






L949 



THEATER TELEVISION 



333 



Table I tabulates these charges for the service between certain prin- 
cipal cities. These same charges apply to intercity relay of television 
programs over microwave relay facilities. 
Returning to our typical theater television operation in Cities A and 

TABLE I 
A. T. AND T. INTERCITY COAXIAL-CABLE RATES (ESTIMATED) 






Service Points 


MONTHLY SERVICE 
Video, 
Allo- 
cated 
(4hrs.) Audio Total 


Video, 
Nonallo- 
cated 
(8hrs.) Audio 


Total 


Boston-New York 


$5,450 


$1,290 


$6,740 




$7,650 


$1,290 


$8,940 


New York-Philadelphia 


2,775 


648 


3,423 




3,905 


648 


4, 


553 


Philadelphia-Baltimore 


2,950 


690 


3,640 




4,150 


690 


4, 


840 


Baltimore-Washington 


1,600 


366 


1,966 




2,260 


366 


2, 


626 


Washington-Richmond 


3,150 


738 


3,888 




4,430 


738 


5, 


168 


Richmond-Charlotte 


6,900 


1,638 


8,538 




9,680 


1,638 


11, 


318 


New York-Pittsburgh 


8,500 


2,022 


10,522 




11,920 


2,022 


13, 


942 


Pittsburgh-Cleveland 


3,550 


834 


4,384 




4,990 


834 


5, 


824 


Cleveland-Detroit 


2,975 


696 


3,671 




4,185 


696 


4, 


881 


Detroit-Chicago 


6,600 


1,566 


8,166 




9,260 


1,566 


10, 


826 


Chicago-Milwaukee 


2,725 


636 


3,361 




3,835 


636 


4, 


471 


Chicago-St. Louis 


7,450 


1,770 


9,220 




10,450 


1,770 


12, 


220 


St. Louis-Kansas City 


6,575 


1,560 


8,135 




9,225 


1,560 


10, 


785 


New York-Los Angeles 


61,650 


14,778 


76,428 




86,330 


14,778 


101, 


108 


OCCASIONAL 


SERVICE 












Each 


Additional 


Hour 




1st 


Hour in 


Month 






in Month 






Service Points 


Video 


Audio 


Total 


Video 


Audio 


Total 


Boston-New York 


$610 


$72.00 


$682. 


00 


$210 


$32.00 


$242 


.00 


New York-Philadelphia 


503 


55.95 


558. 


95 


103 


15.95 


118 


.95 


Philadelphia-Baltimore 


510 


57.00 


567. 


00 


110 


l/.OO 


127 


.00 


Baltimore- Washington 


456 


48.90 


504. 


90 


56 


8.90 


64 


.90 


Washington-Richmond 


518 


58.20 


576. 


20 


118 


18.20 


136 


.20 


Richmond-Charlotte 


668 


80.70 


748. 


70 


268 


40.70 


308 


.70 


New York-Pittsburgh 


732 


90.30 


822. 


30 


332 


50.30 


382 


.30 


Pittsburgh-Cleveland 


534 


60.60 


594. 


60 


134 


20.60 


154 


.60 


Cleveland-Detroit 


511 


57.15 


568. 


15 


111 


17.15 


128 


.15 


Detroit-Chicago 


656 


78.90 


734. 


90 


256 


38.90 


294 


.90 


Chicago-Milwaukee 


501 


55.65 


556. 


65 


101 


15.65 


116 


.65 


Chicago-St. Louis 


690 


84.00 


774. 


00 


290 


44.00 


334 


.00 


St. Louis-Kansas City 


655 


78.75 


733. 


75 


255 


38.75 


293 


.75 


New York -Los Angeles 


2858 


409.20 


3267. 


20 


2458 


369.20 


2827 


.20 



334 McCoy AND WARNER October 

B, and assuming that City A on the coaxial cable is located 89 miles 
from the nearest network city, and that City B is located 35 miles 
from City A, the monthly charges for use of Bell System facilities for 
receiving television programs would include: 6 City A would pay a 
monthly charge of $4840 for use of 240 hours per month on an 8-hour 
per day basis, or $3640 for 120 hours per month on a 4-hour per day 
basis, if the channel were shared with another theater television group 
or a television broadcast station in City A. Likewise, if the theater 
television group in City B utilized a Bell System microwave relay 
system to obtain programs from City A, it would pay a monthly 
charge of $2626 for use of 240 hours per month on an 8-hour per day 
basis or $1966 for the shared use of the channel on a 4-hour basis. 

Concern over the economic problems raised by the A. T. and T. co- 
axial cable rates led the Television Broadcasters Association, Inc. 
(TBA), to file a petition with the FCC requesting suspension of the 
rates, and a hearing upon the reasonableness of the rates and legality 
and other provisions of the tariffs filed. On April 28, 1948, the FCC 
ordered the hearing, but refused to suspend the rates. A determina- 
tion on the reasonableness of the rates 'has been postponed indefinitely. 

Meanwhile, in the same proceeding (Docket 8963) the FCC has 
taken evidence and is considering one of the issues which also is of con- 
cern to theater television. This issue involves the validity of the 
provision in the A. T. and T. tariff that a customer may not connect 
intercity channels of the telephone company with intercity channels of 
others except where the telephone company cannot make facilities 
available upon reasonable notice. 7 If sustained by the FCC, this pro- 
vision would effectively preclude the use of intercity radio-relay 
facilities built by the theater television groups, such as the radio relay 
contemplated in Fig. 1 between City A and City B. It would also 
limit the use that theater television might make of the radio-relay 
facilities offered on a common-carrier basis by Western Union. 

The substantial capital costs required for construction of intercity 
coaxial-cable installations, together with other difficulties, appear to 
make it improbable that theater television will turn to the construc- 
tion of its own intercity coaxial cable to provide a national theater 
television service. According to A. T. and T.'s o\vn figures, submitted 
to the FCC, by the end of 1948, about 4600 miles of intercity tele- 
vision channels had been put into operation at a cost of approxi- 
mately $20,000,000. These figures include the A. T. and T. intercity 
radio-relay circuits described hereafter. 



1949 THEATER TELEVISION 335 

Intercity Radio -Relay Services The second method available today 
for intercity relay of television programs is afforded by microwave 
radio relays. Radio relays constructed by A. T. and T. extend the 
coaxial-cable system from New York to Boston, from Toledo to De- 
troit, and from Chicago to Milwaukee. A. T. and T. has a radio relay 
under construction between New York and Chicago, and has applied 
for FCC consent to construct other radio relays between San 
Francisco and Los Angeles. In addition, Western Union has a radio- 
relay system available for use between New York and Philadelphia, 
and contemplates an extension of its system to the Midwest and 
South. These radio relays are operated on a " common-carrier" basis 
and are open to use by television broadcasters under tariff schedules 
filed with the FCC. The A. T. and T. rates are the same as those in 
effect for coaxial-cable intercity service. The Western Union rates 
are somewhat different. Other privately owned and operated radio 
relays are in operation in various localities. 

The A. T. and T. intercity radio relays operate on the frequency band 
3700 to 4200 megacycles, and the Western Union relays operate on 
5925 to 6425 megacycles. Both these bands are allocated by the FCC 
to "Common-Carrier Fixed Circuits." The A. T. and T. relays can 
provide a bandwidth of 4 megacycles, while the Western Union New 
York to Philadelphia relay is equipped to provide a 5-megacycle 
bandwidth. Intercity television relays are based on line-of-sight trans- 
missions from station to station, with intermediate stations separated 
by about 30 miles between cities. The problems involved in theater 
television use of intercity relays are substantially the same as the 
problems stated above as to use of the coaxial cable. 

Bell System Telephone Wires The third available system for trans- 
mission of television programs is the use of so-called "balanced" tele- 
phone wires. A network of such telephone wires extends under the 
streets of our cities, and across the continent operated by the Bell 
System telephone companies. Over moderate distances of from one to 
two miles, these telephone wires may be adapted to the purpose of 
television transmission. They thus are useful for intracity transmis- 
sion, including remote pickup, STL, and possibly as the basis for a 
multiple-addressee system. The telephone wires may also prove to be 
the most economical method for distribution of theater television 
sound. 



336 McCoy AND WARNER October 

VII. RADIO FREQUENCIES FOR THEATER TELEVISION 
As we have seen, radio frequencies may be expected to constitute 
an integral part of a theater television system under present con- 
ditions. Remote pickups of sports and news events are dependent 
upon microwave frequencies, since only by use of radio relay can 
theater television pickup units get the necessary mobility and flexi- 
bility. Multiple-addressee systems for simultaneous distribution of 
programs to numerous theaters could use coaxial cables or even paired 
telephone wires, but there is- no assurance that the telephone company 
will be in a position to furnish these services, or that the rates for the 
service would be within reach of potential theater television systems. 
It is also possible that theater television will consider the establish- 
ment of an intercity relay system using radio. 

Under the Communications Act, the use of radio frequencies by 
theater television or by any other nongovernmental service must be 
preceded first by the allocation by the FCC of a frequency band or 
bands for the use of theater television; second, by the promulgation 
by the FCC of rules and regulations governing the assignment and 
use of the allocated frequencies by individuals or organizations within 
the service; and third, by the assignment by the FCC of the frequen- 
cies within the general band allocated to theater television to licensees 
upon proper application. 

Theater television has never jumped the first hurdle. It has never 
obtained an allocation of frequencies by the FCC for other than ex- 
perimental use. At the present time, no frequencies are even avail- 
able under the FCC allocation table and rules for experimentation by 
theater television for the purpose of developing this new service, ex- 
cept the 475- to 890-megacycle band (ultra-high-frequency) which is 
earmarked for television broadcasting, and the frequency bands 16,000 
to 18,000 megacycles and 26,000 to 30,000 megacycles, for which no 
equipment is available for the purpose of theater television relays. 
The five theater television authorizations now in existence (four of 
which are held by Paramount Pictures, Inc., and one by 20th Century- 
Fox) are solely experimental special temporary authorizations 
(STA's), issued for 90-day periods, and terminable by the FCC without 
advance notice. These authorizations are for frequencies allocated 
either to the use of television broadcast stations, not to theater tele- 
vision, a distinct and separate service, or to various nonbroadcast 
services. Theater television cannot expect to use these frequencies for 
a regular theater television service. 



1949 THEATER TELEVISION 337 

The motion picture industry since 1944 has made sporadic efforts to 
obtain the allocation of relay frequencies to theater television by the 
FCC. The first such bid, spearheaded by Paul J. Larsen on behalf of 
the Society of Motion Picture Engineers, was made in the general 
allocation hearings held in the fall of 1944 and the spring of 1945 when 
the end of the war was in sight. 

The general allocation hearing (FCC Docket 6651) covering the 
"Allocation of Frequencies in the Radio Spectrum from 10 Kilocycles 
to 30,000,000 Kilocycles" was an open invitation to all who desired to 
obtain new frequencies or the recognition of new radio services to 
come before the FCC and present their cases. The hearing was the 
greatest in scope ever held by the FCC or its predecessor, the Federal 
Radio Commission. Two hundred and twenty-three witnesses, plus 
FCC staff members, appeared and testified. Claims for frequencies 
were presented by some 30 services, including many new radio 
services. One witness, Mr. Larsen, appeared for theater television. 
It is interesting to note that 26 witnesses appeared for television 
broadcasting, 22 for forestry and conservation radio, 17 for police 
radio, and 12 for commercial frequency-modulated broadcasting. 

Mr. Larsen, on behalf of the SMPE, requested for theater television 
an allocation of 1500 megacycles in 20-megacycle-wide channels in 
the radio spectrum between 300 and 6300 megacycles for the "im- 
mediately necessary postwar Theater Television service." This 
recommendation was keyed to the situation in New York City where 
Mr. Larsen stated 25 independent producing and exhibiting agencies 
might compete in the theater television service. For the initial 
period, however, he assumed that 15 of these agencies should be pro- 
vided with frequencies, including for each of the 15 agencies one re- 
mote pickup channel, one studio-transmitter channel, one multiple- 
addressee channel, and one intercity relay channel. Mr. Larsen took 
the position that coaxial cable and wire facilities were not sufficient 
for the multiple-addressee system since channels 20 to 60 megacycles 
wide would be required and only 4 megacycles were available on the 
coaxial cable. Mr. Larsen presented the argument that, in view of 
the relative size and importance of the motion picture industry 
($1,600,000,000 gross income compared to $280,000,000 gross income 
for the broadcast industry) theater television should be treated on a 
"parity of opportunity" with radio broadcasting. By this phrase he 
meant "an equality of opportunity to develop both arts" giving each 
"equal opportunity to experiment, to commercialize, to improve, and 
to expand to its proper and demonstrable limits." 






338 McCoy AND WARNER October 

In its final report of May 25, 1945, in the general allocation hearing, 
the FCC allocated certain frequency bands to theater television on a 
shared basis with other services for experimental use only. It made 
no exclusive allocation to theater television. The bands on which ex- 
perimental theater television were permitted included the 480- to 920- 
megacycle band (on which experimentation with multiple-addressee 
systems was permitted), subject to the understanding "that the band 
480 to 920 megacycles will be used primarily for television broadcast- 
ing to the public, with higher frequencies being more properly utilized 
by theater television and relay operation." In addition, the following 
bands, allocated to the Fixed and Mobile service were made * 'available 
for theater television experimental use, including multiple-addressee 
purposes if the need for such use can be established": 1325 to 1375; 
1750 to 2100; 2450 to 2700; 3900 to 4400; 5650 to 7050; 10,500 to 
13,000; 16,000 to 18,000; and 26,000 to 30,000 megacycles. The 
FCC's final report thus opened the door for theater television experi- 
mentation in a large portion of the radio spectrum. As a practical 
matter, however, even in 1949 equipment is available for radio relay 
only on the frequencies up to the 7000-megacycle band, and equip- 
ment is actively being developed in the 10,000- to 13,000-megacycle 
band. Development of equipment for use in the 16,000- and 26,000- 
megacycle bands must await the future. 

The 1945 allocations in the spectrum between 1000 and 13,000 
megacycles did not remain "final" for long. In November, 1945, the 
4000- to 4200-megacycle band was allocated to Air Navigation Aids. 
In July, 1946, the FCC proposed an extensive reallocation of fre- 
quencies in the 1000- to 13,000-megacycle band. A hearing was held 
on this proposal, as amended October 22, 1946, and Mr. Larsen again 
testified on behalf of theater television and the SMPE on February 4, 
1947. He took the position that theater television should be classified 
by the FCC as a " common-carrier" service, entitled to use the fre- 
quencies allocated to "Common-Carrier Fixed Circuits." If this 
classification was not made by the FCC, Mr. Larsen objected to the 
proposal of the FCC that television pickup and STL stations "will be 
licensed only to licensees of television broadcast stations and to 
common carriers." Finally, Mr. Larsen objected to the failure of the 
FCC to include in its proposal frequencies for intercity television 
relay, which the FCC stated could not be accommodated in the 1000- 
to 13,000-megacycle band since there was not sufficient spectrum 



1949 THEATER TELEVISION 339 

space available. In addition, Mr. Larsen urged the FCC to classify 
theater television as a separate nonbroadcast service. 

On the important question of whether theater television could use 
coaxial cable or wire lines for intercity or intracity transmission of 
programs, Mr. Larsen stated that at the present time theater tele- 
vision would not be able to use coaxial-cable or wire facilities of the 
A. T. and T. because the 2.7-megacycle band provided by A. T. and T. 
was insufficient for theater television. He estimated that approxi- 
mately 6- or 7-megacycle-wide bands would be required. He con- 
ceded that eventually it would be more economical in a city to dis- 
tribute programs by wire line, rather than by radio, and that even- 
tually the common carriers would have wider-band coaxial cable and 
wire facilities. But he felt that for an indefinite period theater tele- 
vision would have to use radio for program distribution. 8 

The upshot of the 1947 allocation hearing was to make no allocation 
in the 1000- to 13,000-megacycle band for theater, television, even on 
an experimental basis, and to indicate that the experimental author- 
izations in this band for operation on frequencies not allocated to the 
service involved might be "renewed on a strictly temporary basis for 
a period not to exceed one year from February 20, 1948." These con- 
clusions were contained in the FCC's report of February 20, 1948 
(Docket 6651), in which the Commission stated that, "The require- 
ments for theater television are still not sufficiently clear to indicate the 
need for a specific allocation for its exclusive use at this time. The Com- 
mission is of the opinion, from information now available to it, that a 
large part, if not all, of the functions required by theater television should 
be handled by stations authorized to operate on frequencies allocated to the 
use of communications common carriers."* 

The FCC ruling, however, has not completely terminated theater 
television experimental use of radio frequencies. Since November 18, 
1947, Paramount Pictures, Inc., has held special temporary authoriza- 
tions for theater television relay in the New York area (in the 
2000- and 7000-megacycle bands), and it was granted two additional 
temporary authorizations on May 4, 1948, for use of the 7000-mega- 
cycle band in the New York area. Likewise, in September, 1948, 20th 
Century-Fox Film Corporation was granted an experimental STA 
for theater television relay in New York in the 7000- and 12,000- 
megacycle bands. 

It is apparent from the above discussion that theater television is at 
the crossroads. It must determine its own future by deciding four 



340 McCoy AND WARNER October 

main questions: (1) Will theater television rely on radio, coaxial 
cable, or wire for intercity and intracity distribution of programs? 
(2) If radio frequencies are to be used by theater television, does it de- 
sire the FCC to allocate frequencies for the use of theater television or 
does theater television expect to use the frequencies allocated to 
"Common-Carrier Fixed Circuits," relying on the existing common 
carriers to provide service to theater television? (3) If radio fre- 
quencies are needed, and theater television is not content to rely on 
the services of established common carriers, what steps should it take 
to obtain the use of such frequencies? (4) If theater television is to 
use common-carrier radio coaxial cable and wire lines, what steps 
should it take to obtain the use of such facilities? 

If theater television groups decide to apply to the FCC for alloca- 
tion of radio frequencies to theater television, or for authorization as a 
television common carrier, they must sustain the burden of convincing 
the FCC that a grant of their requests will serve the public interest, 
convenience, or necessity. In meeting this burden, theater television 
must establish to the satisfaction of the FCC : 

1. That the service requires the use of radio frequencies, and that 
coaxial cable and wire lines will not provide a practical substitute. 

2. That the frequencies requested are not more urgently needed 
by other radio services, particularly those services necessary for safety 
of life and property. 

3. That there is a substantial public need for the service, and a 
strong likelihood that the service will be established on a practical 
working basis. 

In prior appearances before the FCC, theater television has not met 
the burden of proof in these matters. It seems clear that another 
attempt to secure FCC authorization of the service and allocation of 
frequencies should be preceded by active steps by the motion picture 
industry to obtain quantitative data on the public acceptance of 
theater television, and to obtain definite commitments from qualified 
theater television groups in as many areas as possible to the effect that 
they have positive plans to institute the service at an early date. 
Data obtained by actual experimentation with a multiple-addressee 
theater television system would be advisable. A clear indication of 
how theater television could serve the public interest is essential. In 
the latter connection, it is suggested that a multiple-addressee system, 
serving not only privately owned theaters, but rendering service on a 
public-service basis to local, religious, educational, and governmental 



1949 THEATER TELEVISION 341 

groups in the area, could present a strong showing of service to the 
public. Television broadcast stations are not available in sufficient 
numbers to make possible their ownership by any substantial number 
of religious, educational, or civic groups. Theater television poten- 
tially is one means whereby such public service organizations may 
participate directly in the wonders of television. 

On June 30, 1949, the FCC addressed letters to Paramount Tele- 
vision Productions, Inc. , Twentieth Century-Fox Film Corporation, 
and the Society of Motion Picture Engineers, inviting statements to 
be submitted by September 2, 1949, concerning theater television. 
Without limiting the scope of the statements, the Commission re- 
quested expression of views covering six specific subjects: 

1. What the minimum frequency requirements would be for a 
nation-wide, competitive theater television service; 

2. What specific frequency bands you would propose to be allo- 
cated to a theater television service; reasons therefor; 

3. The exact functions which would be performed in each such 
frequency band in a theater television service; 

4. Whether and to what extent such functions could be performed, 
in whole or in part, by use of coaxial cable, wire, or other means of 
transmission not using radio frequencies; 

5. Whether and to what extent existing common carriers have or 
propose to have facilities available capable of performing such func- 
tions, in whole or in part, by radio relay, coaxial cable, or wire; 

6. Plans or proposals looking toward the establishment of a 
theater television service. 

Organization of Co-operative Groups To make theater television 
economically feasible it may be necessary for numbers of theaters in a 
city to join together in co-operative theater television groups. Since 
these groups in all likelihood will find it necessary to qualify as licen- 
sees of radio facilities, and possibly as common carriers of television 
programs, it is important that these co-operative groups be owned and 
organized to comply with the licensing requirements of the Com- 
munications Act and the FCC. 10 

An example of a co-operative organization that is operating in the 
common-carrier field with FCC sanction is Press Wireless, Inc. This 
corporation was organized in 1929 r with its stock held primarily by 
newspaper and news associations. It has been licensed or authorized 
by the FCC to engage in various forms of communications, including 
program transmission, radiophoto, facsimile, and message telegraphy. 



342 McCoy AND WARNER October 

It conducts a public-press service on a multiple-addressee basis, trans- 
mitting news items and other material intended for publication by 
press agencies and newspapers. Similarly, a theater television group 
might be organized to provide a limited common-carrier service to 
theaters, educational, and public-service organizations. 

VIII. COLOR TELEVISION 

From the early beginnings of television, the idea of television in 
color has intrigued the imagination. As the motion picture industry 
has discovered, the mere fact that a production is offered in color 
rather than in black and white increases the public's interest and 
makes for far greater salability. In the television field, the first 
proponent of color was the Columbia Broadcasting System, Inc., 
which for many years operated both black-and-white and color 
stations in New York City. Shortly after the end of hostilities, CBS 
felt that its color-television system was ready to emerge from the 
laboratory and experimental stage, and on September 27, 1946, it 
petitioned the FCC to promulgate rules and engineering standards 
authorizing commercial television in color in the ultra-high-frequency 
band (480 to 920 megacycles). 11 The CBS proposal, based on de- 
velopmental work by CBS's Peter Goldmark at a cost of some 
$2,000,000, looked toward the creation of 27 color television channels 
in the ultra-high-frequency band, each channel being 16 megacycles 
wide. This proposal would have appropriated substantially all of 
the ultra-high frequencies for color television. 

After lengthy hearings on the CBS proposal, the FCC on March 18, 
1947, denied the petition, primarily for the reason that "many of the 
fundamentals of a color-television system have not been adequately 
field-tested and that need exists for further experimentation." The 
FCC commended CBS and Dr. Goldmark for their great strides made 
in the field, and concluded: "It is hoped that all persons with a true 
interest in the future of color television will continue their experimen- 
tation in this field in the hope that a satisfactory system can be de- 
veloped and demonstrated at the earliest possible date." 12 

The CBS proposal contemplated authorization of the so-called se- 
quential system in which each picture is scanned through separate 
color filters red, green, and blue, in turn. Under that proposal the 
transmissions in the separate colors followed each other at the rate of 
48 per second. The three colors were accepted by the receiver by 
means of a color wheel containing filters of red, green, and blue, which 



1949 THEATER TELEVISION 343 

rotates in front of the television screen in synchronization with a simi- 
lar color wheel at the transmitter. The eye saw the picture in full color. 
At the same hearing, RCA gave evidence concerning a different sys- 
tem of color television but did not request the FCC to approve its sys- 
tem at that time. In the RCA system, known as the simultaneous 
system, each picture was scanned simultaneously in three colors red, 
green, and blue and these transmissions were sent simultaneously on 
three different channels and were combined at the receiver to produce 
a color image. 

After the issuance of the March, 1947, report denying CBS's color 
proposal, CBS turned its attentions in the television field mainly to 
the building of its monochrome network. But both CBS and RCA 
continued color experiments. In October, 1948, CBS demonstrated to 
FCC staff members a sequential color system, using only 6 mega- 
cycles of bandwidth. The system could be operated either with a 
rotating color drum or with stationary color filters. At the same time 
CBS demonstrated that an ordinary commercial 10-inch table tele- 
vision receiver (monochrome) could be converted so as to receive the 
color transmissions either in black and white or in color. 

Interest in color television flared brightly in May, 1949, when the 
FCC issued a public notice in which it stated that in reopening the 
pending television allocation proceedings it planned "to afford an 
opportunity for the submission of proposals looking toward utilization 
of all television channels (both very-high-frequency and the ultra- 
high-frequency) to 6 megacycles monochrome or color on an optional 
basis in such a way as to permit reception on the ordinary television 
receiver with relatively minor modifications." Following up this 
announcement, the FCC on July 11, 1949, issued its notice of further 
proposed rule-making in the allocation proceedings and stated defi- 
nitely that it would give consideration to proposals for color television 
on both the very-high-frequency and the ultra-high-frequency tele- 
vision channels, provided that any such proposal must permit opera- 
tion in a 6-megacycle channel and must be such that existing tele- 
vision receivers will be able to receive color transmissions "simply by 
making relatively minor modifications in such existing receivers." In 
a recent speech, one FCC Commissioner explained that the FCC 
rould not authorize color (1) until color can be received satisfactorily 
>n today's ordinary television receiver with only relatively minor 
lodifications, and (2) until color-television pictures can be received 
black and white on present-day receivers, with perhaps no, or only 
datively minor, modifications. 



344 McCoy AND WARNER October 

While it is impossible to predict what evidence concerning color 
television will be presented to the FCC in the now scheduled hearings, 
and it is likewise impossible to foretell what action the FCC will take 
on color television, the motion picture industry obviously must con- 
sider color in connection with its planning concerning theater 
television. 

Not only must theater television interests be aware that broadcast 
television in color will be a much stronger competitor than black-and- 
white television, but they must take into account that theater tele- 
vision in color may well be much more attractive to the public than 
either monochrome film or monochrome theater television. Theater 
television in color, therefore, deserves careful investigation by the 
theater television interests. Such an investigation may reveal that 
theater television in color holds sufficient promise of becoming a box- 
office attraction in its own right to justify the conclusion that the 
motion picture industry should enter the theater television field on a 
broad scale. 

From the technical viewpoint, color would require further develop- 
ment of the theater television equipment mentioned in this article, but 
it is not unreasonable to expect that color could be adapted to theater 
television with at least no greater difficulty than it could be applied to 
broadcast television. 

Theater television in color would also have its impact on the fre- 
quency-allocation problems now facing theater television. While it 
appears that broadcast color television, if sanctioned by the FCC, will 
be limited to a 6-megacycle bandwidth, the theater television in- 
terests will be forced to inquire whether they should limit their in- 
terests in color to a system of this bandwidth. The advantages of a 
wider bandwidth, including greater definition, greater frame rate, 
greater picture brightness, and less flicker, may well make it desirable 
for theater television to seek more than a 6-megacycle band for theater 
television relays. However, before a bandwidth wider than 6 mega- 
cycles is adopted for theater television it will be necessary to consider 
whether the existing common-carrier facilities for intercity relay of 
television programs could be adapted for such a wide-band video 
transmission. 

Color television faces many obstacles before it can be expected to 
take its place beside monochrome television. But the place it holds in 
the imagination of the public makes it a factor to be considered care- 
fully by the motion picture industry. 



1949 THEATER TELEVISION 345 

IX. PROGRAMMING 

The foregoing discussion indicates that theater television is tech- 
nically feasible and within the pocketbook range of the majority of 
exhibitors. Our next inquiry is what can be done with a co-operative 
system of theater television from a programming standpoint, will 
theater television be economically feasible and can it compete with 
television broadcasting, and what effect and impact will theater tele- 
vision have on motion pictures and television broadcasting. A word 
of caution is appropriate at this time. Theater television is just 
emerging from the laboratory stage; its experimental phase is just 
about to begin. We have no statistical data to buttress our conclu- 
sions. The latter are of necessity tentative and may warrant re- 
vision in the light of future developments. 

Program material for theater television can be derived from : 

1. Television broadcasting, or 

2. Independent sources. The latter term has reference to pro- 
grams secured by and through the co-operative group engaged in 
theater television. 

If the co-operative group seeks program material from the television 
broadcast station or network, it is beset with certain legal problems. 

Section 325 (a) of the Communications Act of 1934 prohibits a 
station from rebroadcasting the programs of another broadcast station 
without the express authority of the originating station. This tenders 
the question of whether the pickup and ; transmission of a television 
program to a theater is a "rebroadcast" requiring the permission of the 
originating station. This point has not been adjudicated either by 
the FCC or the courts. It is believed that when Section 325 (a) was 
enacted into law, it was the intention of Congress that the originating 
station or system should have the right "to control its program after 
it has been thrown onto the air." This suggests that the co-operative 
group of television theaters would be required to secure the permission 
of the television broadcast station or network. 

In the event that Section 325 (a) is construed by the FCC and the 
courts as not to require the consent of the originating station, the 
theater television group would be precluded by common law and 
statutory copyright from retelevising the programs transmitted by a 
television broadcast station. The court undoubtedly will hold that 
the production of any television program, i.e., news, sports, variety 
show, and so forth, involving as it does the expenditures of skills in the 
use of the television camera, effort, and monies, results in the 



346 McCoy AND WARNER October 

establishment of a common-law copyright. This common-law copy- 
right is the exclusive property of the station and network and the 
former may prohibit the co-operative group of television theaters 
from retelecasting such programs. Common-law copyright is illus- 
trated by the litigation arising out of the Louis-Walcott fight. A 
Pennsylvania court enjoined a motion picture exhibitor 'from picking 
up and retelecasting the Louis-Walcott fight in his theater, because 
of the common-law copyright in the telecast which was the property 
of the sponsor, network, and station. 

A television station or network can protect its programs by copy- 
righting the same. The copyright of a dramatic program prohibits the 
reproduction of the same unless a license is obtained from the copy- 
right proprietor. The unauthorized exhibition of a copyrighted pro- 
gram would subject each exhibitor to minimum statutory damages of 
$250 for each unauthorized telecast. 

Thus, the co-operative group of television theaters would be pre- 
cluded from using the program material of a television broadcast 
station or network, unless the latter consented. A television network 
might find it economically feasible to make its commercial or sustain- 
ing program service available in theaters for a stipulated fee. On the 
other hand and as will be subsequently developed, theater television 
may be a competitive threat to television broadcasting and the tele- 
vision network may refuse to make its program service available to 
theaters. This means that the latter must obtain its own programs. 
This raises the next question : what independent programs are avail- 
able to the theater television group? 

An excellent source of programming would be local or national news. 
Since a news event, i.e., a political address, parade, or fire, is a public 
event, any organization may transmit its own version of the event to 
the public via television broadcasting or to theaters by theater tele- 
vision. All that is required to carry a news program is a mobile unit 
to transmit the program to the central distribution point, for redis- 
tribution to the theaters. If co-operative theater groups are inter- 
connected on a national scale, outstanding national events such as a 
presidential inauguration could be made available to all theaters. 

A second source of programming is sports events. Thus, boxing 
bouts and baseball and football games could be brought into the 
theater. The use of sports events in theater television tenders certain 
economic and legal issues which warrant discussion. 

Not only are the television broadcast rights to an athletic contest 



1949 THEATER TELEVISION 347 

available for sale to a sponsor, but the promoter likewise may sell the 
theater television rights to a co-operative group. The question ten- 
dered is whether it is economically feasible for the television broadcast 
sponsor and the theater television group to carry the same program. 
If a boxing bout can be viewed on home television receivers, there 
would be no need to attend a motion picture house which would carry 
the same program. On the other hand, the motion picture exhibitor 
could integrate the boxing bout into his scheduled evening show and 
thus offer an added attraction to his patrons. Whether the television 
broadcast of an athletic event would curtail the box-office returns of 
the theater television group, carrying the same sports program, can- 
not be answered at this time. We have neither the data nor experience 
to buttress our conclusions. 

But suppose 10,000 exhibitors were to band together and purchase 
on an exclusive basis the television rights to the World Series. The 
cost of such exclusive rights could be defrayed by an admission 
charge to view the World Series. In this connection, there are in ex- 
cess of 19,000 theaters in the United States; their total seating ca- 
pacity is close to 12,000,000 seats; their monthly revenues are in ex- 
cess of $100,000,000; their yearly revenues produce a minimum reve- 
nue of $1,500,000,000. Compare these figures with an approximate 
$500,000,000 yearly gross broadcast revenues. It is apparent that the 
theater television group could outbid the television broadcast industry 
for the right to exhibit the World Series. Whether there will be com- 
petitive bidding between theater and broadcast television cannot be 
determined at this time. Theater television does not exist on a local, 
let alone national, level. We do know that television broadcasting, 
particularly in the East, is one of the factors which has caused a 
diminution in the box-office returns of motion picture houses. It may 
well be that theater and broadcast television are noncompetitive. 
But certainly the theaters must do something to offset their diminish- 
ing box-office returns. Theater television may be the answer. 

A third source of programming for theater television is "live" acts. 
This term has reference to variety or vaudeville shows, concerts, and 
plays. Theater television would enable all members of a co-operative 
group or theater chain in a city to furnish their patrons with vaude- 
ville. Thus, a variety show could be presented in a local neighborhood 
theater as well as in a "downtown showcase." Since programs for 
theater television can be distributed via film, the latter gives flexi- 
bility to the program schedule of a motion picture house engaged in 
theater television. 



348 McCoy AND WARNER October 

The financial resources of the theater television group on a national 
scale, suggest that it could sponsor a repertory company which would 
produce different plays each week. An exhibitor could charge an in- 
creased admission fee for exhibiting such a play. The recording of 
such plays on film would enable the theaters to exhibit the play or 
plays at a time or times convenient to its patrons. 

Theater television is available to enlarge the concert audience. 
Thus, a concert by a distinguished pianist could be made available in 
motion picture houses. Undoubtedly, financial arrangements could 
be effected among the promoter, the concert star, and the exhibitor. 

Theater television likewise may be employed as a new means for the 
distribution of film. Thus, a feature-length attraction could be dis- 
tributed on a national, regional, or local basis to exhibitors. The elec- 
tronic method of distributing motion picture film could furnish the 
producer with an efficient method of "trade-showing" film; it could re- 
duce the number of positive prints, and thus costs. Theater television 
may conceivably result in far-reaching changes in the trade practices 
of the motion picture industry and effect substantial economies in the 
distribution of film. 

Theater television is not limited to entertainment ; it can render a 
public service to the community. Thus, in the forenoon, the theater 
television system in its entirety could be made available to the school 
system. The latter could install receivers in the schools; in addition 
it could use the theaters as classrooms. Lectures and motion pictures 
could be made available to the entire student body of a community. 
It has been suggested that theater television might be the medium or 
means whereby the schools can use television without undertaking the 
costly job of constructing and operating a television broadcast station. 

This discussion indicates that theater television is technically and 
economically feasible, that there aTe adequate sources of program ma- 
terial which can and will be made available to the theater television 
group. Theater television will stimulate and help the box-office re- 
turns of the. motion picture exhibitor. Theater television which is 
nonexistent today constitutes no economic threat to television broad- 
casting. But if theater television is organized on a local, regional, and 
national basis, it could .become a challenge to television broadcasting. 

Whether theater television ever will achieve its potentialities as an 
entertainment and public-service medium depends on the willingness 
and determination of the motion picture industry to develop this new 
art. Failure to accept this opportunity may well spell the doom of 



1949 THEATER TELEVISION 349 

theater television since the motion picture industry has the resources 
id can adapt its technical knowledge to this new art. The time to act 
now. 



APPENDIX 

(1) Other uses of television by the motion picture industry might include (1) 
lership of television broadcast stations, and (2) development of pay-as-you-see 
^vision schemes such as Zenith Radio Corporation's "Phonevision." 

(2) Electronic-storage, as opposed to film-storage, methods are also under de- 
velopment, using the Skiatron tube (or P10 phosphor) and the so-called^ Swiss or 
AFIF Method, developed by Dr. F. Fischer of the Swiss Federal Institute of 
Technology. Electronic-storage methods, however, are not expected to be avail- 
able for commercial use in the near future. 

(3) A similar direct projection system has been developed in England. See 
A. G. D. West, "Development of theater television in England," J. Soc. Mot. Pict. 
Eng., vol. 51, pp. 127-169; August, 1948. 

(4) The 20th Century-Fox report to the FCC of its experimental theater 
television operations contained the tentative conclusion: "The quality of a tele- 
vision picture having a total of 525 scanning lines per frame and a horizontal 
resolution in excess of 600 lines, with good picture contrast ratio, will approach 
that of 35-mm professional motion picture film, provided there is good half-tone 
reproduction, accurate line interlace, and specified minimum of geometric distor- 
tion. Such a value of horizontal resolution would require a video band-pass of be- 
tween 7 and 8 megacycles." 

(5) See 2 FCC Reports 308. 

(6) The airline distance from Philadelphia to Baltimore is about 89 miles; 
from Baltimore to Washington, D. C., is about 35 miles. 

(7) By A. T. and T. tariff filings made on January 14, 1949, effective March 1, 
1949, this restriction on interconnection was relaxed somewhat. For example, if 
the customer orders service for a period longer than three months, in an area where 
the telephone company has no intercity channel facilities, the customer must 
give the telephone company 12 months' notice. But he will be informed within 
three months whether it will have facilities between the service points within a 
year. If such facilities will not be available, the customer may connect his 
facilities with those of the telephone company until three years from the service 
date, and he may continue to connect thereafter until the telephone company has 
facilities, subject to three months' notice from the telephone company. However, 
the FCC has suspended this tariff provision pending its consideration of the re- 
striction on interconnection. 

(8) Former FCC Commissioner E. K. Jett asked Mr. Larsen if any theater 
television was on the air. When Mr. Larsen answered that none was on the air, 
Commissioner Jett, pointing to the other demands for the frequencies in the 1000- 
to 13,000-megacycle band, stated: "Apparently, you would want all the other 
radio services to stop dead in their tracks and wait for the development of theater 
television service until they can go ahead." 



350 McCoy AND WARNER 

(9) Apparently the frequency bands 16,000 to 18,000 and 26,000 to 30,000 
megacycles still remain open for theater television experimentation, but the de- 
velopment of these frequencies is in the embryonic stage. 

(10) Currently the FCC is studying the effect of the decision of the United 
States Supreme Court in United States versus Paramount Pictures, Inc., et al., 
334 U. S. 331, upon the qualifications of the major motion picture companies to 
hold broadcast and television licenses. In that case, Paramount Pictures, Inc., 
Twentieth Century-Fox Film Corporation, Warner Brothers Pictures, Inc., 
Loew's, Inc., and Radio-Keith-Orpheum Corporation were found to have violated 
the Federal antitrust statutes. 

(11) CBS first publicly demonstrated color television in September, 1940. In 
May, 1941, it inaugurated regularly scheduled color-television programs over ex- 
perimental Station W2XAB in New York City operating in the very-high- 
frequency band. In October, 1945, W2XCS resumed color broadcasts from the 
Chrysler Building in New York City operating at about 490 megacycles. CBS 
has also relayed color transmissions between New York City and Washington, 
B.C. 

(12) The FCC Report and Order stated: "Before approving proposed stand- 
ards, the Commission must be satisfied not only that the system proposed will 
work, but also that the system is as good as can be expected within any reasonable 
time in the foreseeable future. In addition, the system should be capable of per- 
mitting incorporation of better performance characteristics without requiring a 
change in fundamental standards. Otherwise, the danger exists that the standards 
will be set before fundamental developments have been made, with the result that 
the public would be saddled with an inferior service, if the new changes were not 
adopted, or if they were adopted, receivers already in the hands of the public 
would be rendered useless. 

"Judged by the foregoing tests, the Commission is of the view that the standards 
for color television proposed by Columbia Broadcasting System should not be 
adopted. In the Commission's opinion the evidence does not show that they 
represent the optimum performance which may be expected of a color-television 
system within a reasonable time. The Commission bases this conclusion on two 
grounds. In the first place, the Commission believes that there has not been ade- 
quate field-testing of the system for the Commission to be able to proceed with 
confidence that the system will work adequately in practice. Second, the Com- 
mission is of the opinion that there may be other systems of transmitting color 
which offer the possibility of cheaper receivers and narrower bandwidths that have 
not been fully explored." The Report expanded on the FCC's view of the need 
for further experimentation follows: "The evidence before the Commission shows 
that 27 channels ultimately may not be enough to provide for a truly nation-wide 
competitive television system. Every effort must, therefore, be made to narrow 
the bandwidth required for color television. It should be emphasized that narrow- 
ing the bandwidth should not be at the expense of picture brightness, picture de- 
tail, color fidelity, or other features of television performance. The objective 
should be a narrower bandwidth while retaining and even improving the quality o: 
television performance." 



FCC Allocation of Frequencies 
for Theater Television* 



Editorial Note: On February 20, 1948, the Federal Communications Com- 
mission issued a Public Notice (48-481, Mimeo. 17266) reporting under 
Docket No. 6651 on radio-frequency allocations to nongovernment services be- 
tween 1000 and 13,200 megacycles, as a result of hearings held on January 15 
and May 26, 1947. On June 29, 1949, the Commission invited the Society, 
Paramount, and Twentieth Century-Fox to file Statements concerning the allo- 
cation of bands of frequencies for commercial theater television service, re- 
questing that these Statements be presented by September 2, 1949. 

THE COMMISSION classifies fixed and mobile services in this region 
in the following categories : 

(1) Common-carrier fixed circuits. In this region television re- 
laying usually would be provided for in such service. 

(2) Fixed circuits except common carrier, television studio-trans- 
mitter links, and interim television relay. These are miscellaneous 
fixed services not in the other categories. 

(3) Mobile, except television pickup. 

(4) Television pickup, television studio-transmitter links, and 
interim television relay. The interim private television-relay service 
is added to this category pending permanent service by common 
carriers. 

On theater television, and regarding the probable permanence of 
the allocations, the report states, "The Commission reaffirms in this 
report its position regarding the specific allocation of frequency bands 
for theater television, as set forth on pages 128 and 129 of the 'Report 
of Allocations issued in Docket No. 6651 on May 25, 1945' (published 
in the JOURNAL, vol. 45, pp. 16-19; July, 1945). The requirements 
for theater television are still not sufficiently clear to indicate the need 
for a specific allocation for its exclusive use at this time. The Com- 
mission is of the opinion, from information now available to it, that a 
large part, if not all, of the functions required by theater television 
! should be handled by stations authorized to operate on frequencies 
allocated to the use of communications common carriers .... 

"The Commission is not convinced that all the services proposing 

* Including a condensed version of a report delivered by Paul J. Larsen on May 
17, 1948, at the SMPE Convention in Santa Monica and a report of more recent 
t action initiated by the Commission on June 29, 1949. 

OCTOBER, 1949 JOURNAL OF THE SMPE VOLUME 53 351 



352 



FCC FREQUENCY ALLOCATION 



October 



to operate in this portion of the spectrum will prove to be justifiable, 
particularly in view of the limited frequency space available for all the 
nongovernment fixed and mobile services. However, the Commis- 
sion is making frequency space available in this manner at this time in 
order to permit experimentation and a demonstration by stations 
in each of the categories of the value and need for the service they 
render." 
The allocations are shown in Table I. 

TABLE I 



Frequency 
Band, Me 


Allocation, Category 


Frequency 
Band, Me 


Allocation, 
Category 


1850-1990 


2 


5,925- 6,425 


1 


1990-2110 


4 


6,425- 6,575 


3 


2110-2200 


2 


6,575- 6,875 


2 


2450-2500 


General fixed and mobile, 


6,875- 7,125 


4 




limited radio-location 


10,700-11,700 


1 






11,700-12,200 


3 


2500-2700 


2 


12,200-12,700 


2 


3500-3700 


3 


12,700-13,200 


4 


3700-4200 


1 







The February 20, 1948, Public Notice of the FCC on radio fre- 
quencies for theater television use was the second of three such ac- 
tions with which the SMPE has been concerned. The first was a 
Public Hearing held in 1944 and the third was initiated by the Com- 
mission by its letters of June 29, 1949, addressed to the Society, 
Paramount, and Twentieth Century-Fox. The Commission, in 
these letters and in its Public Notice 37951, dated July 1, 1949, asked 
that the Society and the two motion picture companies file State- 
ments with the Commission by September 2, 1949, outlining the 
industry's need for allocation of bands of frequencies for theater 
television use. This time, operation of such a service was to be 
considered on a commercial basis, however, rather than experimental i 
as before. 

In the eight weeks which followed receipt of the FCC request,! 
the SMPE Theater Television Committee, under the Chairmanship j 
of D. E. Hyndman, prepared such a Statement, outlining the public-| 
service aspects of a nation-wide theater television system, the physical! 



1949 FCC FREQUENCY ALLOCATION 353 

nature of such a system, and the immediate and future needs of our 
industry for theater television frequencies. 

The Report which appears on the following pages was filed with 
the Commission on August 29, 1949, and requests that the Federal 
Communications Commission allocate a broad band of radio fre- 
quencies which should ultimately be assigned as a number of specific 
theater television channels to individual exhibitor, producer, or 
distributor companies. 

The Society has thus undertaken to point the way for growth of a 
theater television service and to provide the Commission with a 
broad general picture of a nation-wide theater television service, 
furnishing such technical details as the Commission will require in 
order to make its basic decisions of policy. The Statement, per se, 
is a single communication from one group within the industry. To 
insure further that the entire motion picture industry's views are 
presented and that those views favoring the allocation of bands of 
theater television frequencies at this time are in substantial agree- 
ment, the Society has asked industry associations and groups of pro- 
ducer, distributor, and exhibitor companies to endorse the stand 
which the Society has taken. 

Also, to insure an adequate Statement of the industry's position 
before the FCC, the Society asked these organizations 

1. To endorse the SMPE's- formal Statement. 

2. Outline the benefits that would accrue to the American public 
from the formation of a theater television service. 

3. Request an FCC Public Hearing on the matter in the near 
future. 

The Motion Picture Association, a trade group of motion picture 
producing and distributing companies; the Theatre Owners of 
America, an association of independent exhibitors; and the Society 
have all made their views clear to the Commission by filing State- 
ments within the time limit established and the industry is now 
awaiting further action by the FCC. 



Statement on 
Theater Television 



This statement was prepared by the Theater Television Committee of the 
Society of Motion Picture Engineers, under the chairmanship of Donald E. 
Hyndman, and was filed with the Secretary of the Commissian on August 
29, 1949. 



THIS STATEMENT is in reply fco a letter from the Federal Communi- 
cations Commission dated June 29, 1949, concerning the allocation 
of frequencies for theater television. In its letter and in Public Notice 
37951, dated July 1, 1949, the Commission asked that the Society 
of Motion Picture Engineers answer six questions relating to a 
nation-wide theater television service. 

The Society's answers presented here are intended to demonstrate 
the importance to the American public of such a service and are based 
on four prime considerations. 

Point 1 The motion picture industry in years past has provided 
ready communications with the peoples of the United States through 
the medium of film. During times of emergency, this medium has 
been exploited for purposes of public morale and governmental infor- 
mation essential to our national welfare and economy. A nation-wide 
theater television system will be able to render a similar service of 
even greater effectiveness because of its instantaneous nature. 

Point 2 Theater television as a service to the public in general 
is not restricted to any particular group and presents numerous edu- 
cational as well as entertainment possibilities. Events of outstanding 
historical importance or of great social significance may be viewed 
in schools, public auditoriums, and theaters at the moment they occur. 
Thus its appeal to the public, and the likely size of the resultant au- 
dience, are such that the people of the United States as a whole will be 
the beneficiaries of any thoughtfully established, well-maintained, 
and ably administered theater television service. 

Point 3 Theater television is as important as any other entertain- 
ment medium and should receive the same study, sanction, and sup- 
port by the government as any comparable entertainment enterprise. 

Point 4 Theater television deserves the opportunity for develop- 
ment and expansion which is the right accorded any new industry! 
354 OCTOBER, 1949 JOURNAL OF THE SMPE VOLUME 53 



STATEMENT ON THEATER TELEVISION 355 

in the United States. It will afford marked industrial aid to the 
country by providing employment and personal opportunity to many 
people. 

It is desirable to outline briefly the nature of a theater television 
service in order to emphasize more clearly the need for frequency allo- 
! cations. In its simplest form, such a service would consist of one 
'program-originating organization which provides theater television 
! programs to theaters within a given city or within a single market 
I area. Facilities will be required to serve broadly two functions: 
; PICKUP and DISTRIBUTION of programs. These programs must be 
produced, brought to a central point, and then distributed on an 
intracity basis to the various theaters or auditoriums within the area 
served by that particular program-originating organization. If serv- 
ice thus offered locally is to be extended to other cities as well, a third 
function is involved. 

PICKUP Referring to the pickup aspects of programming, if these 
! originate at a point other than the central studios of the program- 
j originating organization, it becomes necessary to carry them from the 
point of origin to the central studio location by flexible and rapid 
procedure. 

DISTRIBUTION Passing to the distribution of the programs from 
the central point to the theaters, an intraurban multiple-addressee 
distribution system is necessary. The channel which carries the 
program from the central point of origin to each of the served theaters 
would be somewhat similar to the multiple-addressee communications 
system used in the distribution of news from a press radio station 
3n land to a multiplicity of ships at sea. 

The distribution system required for theater television will not, 
lowever, be restricted to intraurban operation. In addition to 
serving a given group of theaters, in a specific city or market area, it 
nay be desirable and economical to distribute such programs more 
Droadly. Such interurban channels must carry the picture and 
iccompanying sound from city to city, and ultimately on a nation- 
wide basis. 

TRANSMISSION FACILITIES In order to provide the picture quality 
'equired by the theater, it will be necessary to use radio-frequency 
systems for the transmission of theater television signals. This is 
3articulary true as the art develops and theaters require high defini- 
tion and/or color programs. 



356 STATEMENT ON THEATER TELEVISION October 

It is possible, however, that other types of facilities may become 
available in the future through advanced developments (for example, 
special forms of long-distance wave guides). 

INDUSTRIAL COMPETITION Theater television will endeavor to 
offer material paralleling in a general fashion that presented by the 
legitimate theater, radio, and motion pictures, but adding the impor- 
tant element of immediacy. It will thus add a new medium and 
should stimulate these existing enterprises as well as theater televi-j 
sion. As regards intraindustry competition, there Avill also be un- 
restricted competition among the various program-originating groups. 
It is anticipated that eventually theater television presentations in I 
any given locality will be optionally obtainable by the exhibitors 
from a number of sources, each of whom will offer programs compet- 
ing on the basis of their cost and merit. 

The general facilities required for a nation-wide theater television 
service consist, therefore, of flexible and economical radio channels 
connecting remote program pickup points in each city with central 
studios and transmitters, as well as one or more channels connecting 
transmitters to the theaters which intend to reproduce the programs. 
In addition, channels between cities are required for more extensive 
distribution. 

FCC REQUEST The June 29 letter from the Federal Communica- 
tions Commission to the Society of Motion Picture Engineers said, 
" Without limiting the scope of the statements, the Commission re- 
quests expression of views covering six specific subjects. 

"1. What the minimum frequency requirements would be for a 
nation-wide competitive theater television service; 

"2. What specific frequency bands you would propose to be allo- 
cated to a theater television service; reasons therefor; 

"3. The exact functions which would be performed in each sucW 
frequency band in a theater television service; 

"4. Whether and to what extent such functions could be performed] 
in whole or in part, by use of coaxial cable, wire, or other means onj 
transmission not using radio frequencies; 

" 5. Whether and- to what extent existing common carriers have on 
propose to have facilities available capable of performing suchj 
functions, in whole or in part, by radio relay, coaxial cable, or wire; t 

"6. Plans or proposals looking toward the establishment of then I ci 
television service." 



1949 STATEMENT ON THEATER TELEVISION 357 

Since the answers to some of the above questions are interrelated, 
no attempt has been made to separate them in the following state- 
ment. However, they are summarized briefly and in order, together 
with a few concluding remarks, at the end of this statement. 

The following statements attempt to justify on technical grounds 
the views of the Society of Motion Picture Engineers favoring the 
allocation at this time of frequencies for commercial theater television 
use. Consideration of desirable picture quality and the related 
requirements for bandwidths and channels, as well as various service 
classifications of a nation-wide theater television service, are included. 

PICTURE QUALITY Theater television programs must be presented 
to the public on the basis of picture size and quality not likely to be 
attained in the home. Theater patrons have come to take for granted 
the superior detail and quality of present-day motion pictures and if 
they are to be served adequately, theater television must plan to 
present ultimately television pictures of detail and quality comparable 
to what they have become accustomed to expect. In addition, the- 
ater viewing conditions tend to suppress outside distractions, focusing 
the viewer's attention on the screen with the result that he becomes 
increasingly conscious of structural details of the picture. 

Program material suitable for showing in theaters and auditoriums 
will eventually need the addition of color. Although monochrome 
broadcast service in the home has proved of ^extensive interest to the 
American public so far, and at the outset theater television will also 
be monochrome, the theaters should ultimately present high-quality 
color television pictures in a reasonably advanced state of 
development. 

It should not be assumed that high-detail monochrome or color 
I television for theater use is to be anticipated in the immediate future, 
i On the contrary, theater television should evolve from the present 
[broadcast standards of 525-line monochrome pictures to pictures of 
I greater resolution and in color as new equipment and improved methods 
are made available. It is emphasized that immediate theater tele- 
vision operation must be based on the capabilities of equipment that 
exists today, but if future technical growth which is of critical impor- 
tance to the long-term and stable success of theater television is to 
be allowed, these developments should not be hampered by severely 
restricting channel and bandwidths at this time. 

BANDWIDTHS AND CHANNELS If a competitive nation-wide theater 



358 STATEMENT ON THEATER TELEVISION October 

television service is to be established, it is necessary to have available 
communication or syndicating facilities to distribute programs locally, 
regionally, and on a nation-wide basis from a point of origin. 

At the present state of knowledge of the art, the Society estimates 
that distribution channels 50 megacycles wide will be required to 
transmit high-definition monochrome or color television programs 
satisfactory for theater use. 

It is quite possible that theater television will require up to 60 
channels, at least in the larger metropolitan areas. This allocation 
plan would then provide six channels for each of ten possible program- 
originating organizations. 

In specifying that six channels would be required for each of the 
program-originating organizations, it is believed that each such or- 
ganization would need two channels for program pickup (where 
necessary one of these channels will be employed as a studio-trans- 
mitter link and the other for remote pickup) ; two channels for dis- 
tribution of programs to its theaters (which might well be divided into 
two groups requiring different programs or types of theater television 
at the same time) ; and at least two channels for intercity distribution! 
(in long-distance transmission several relay points are necessary, anc 
it usually is not practicable both to receive and transmit on the same 
carrier frequency from any single relay station) . 

While six channels would provide highly satisfactory distribution, 
it is possible that the two channels used for distribution of programs 
to theaters within a single urban area could also be used for relaying 
programs between cities. Practical answers to this question, how- 
ever, can only be arrived at after experience is gained through future 
commercial operation. 

SERVICE CLASSIFICATIONS The Society is not in a position t( 
estimate the number of types of program-originating organizations 
which should exist to provide a truly competitive nation-wide theateij 
television service. However, in order that the Commission may havd 
some idea of what would be expected with various types of operation 
several possible classes of service are outlined below. Service grades; 
and types, together with a table showing the bandwidths required 
for each type of operation, are included. 

Grade 1 Service Grade 1 program-originating organizations woulc! 
require six channels: Two for remote pickup; two for simultaneous 
transmission of two events or programs to different classes of local 
theaters; and two for intercity connection. 



1949 



STATEMENT ON THEATER TELEVISION 



359 



Grade 2 Service Grade 2 program-originating organizations would 
require three channels : One channel for transmission of programs to a 
local group of theaters; one for remote pickup; and one for intercity 
connection. 

Grade 3 Service Grade 3 program-originating organizations would 
require two channels. This would be a strictly local service since one 
channel would be used for remote pickup and one for transmitting 
programs to a group of theaters. 

Depending upon the size and nature of the community, various 
numbers of program-originating organizations will be necessary. 
They are outlined as follows: 

Type 1 Operation The number of program-originating groups in 
a Type 1 competitive area would be 10. 

Type 2 Operation The number of program-originating groups in a 
Type 2 competitive area would be 6. 

Type 3 Operation The number of program-originating groups in a 
Type 3 competitive area would be 3. 

Based on the foregoing classifications, Table I gives the total num- 
ber of required channels and the total bandwidths which would be 
needed for the various combinations of particular grades and types 
of service. This table is based on the assumption that each channel 
will be 50 megacycles wide. Doubtless most transmission will be 
extremely directional and therefore identical channels may be used in 
relatively near-by cities and towns. Thus it may not be necessary 
to restrict the use of a single channel to widely separated areas as is 

the case with lower-frequency television broadcast channels. 

i 

TABLE I 



Com- 
petitive 
Type 

Grade of 
Service 


Type 

Total 
Channels 


1 
Total 
Band- 
width 


-Type 2- 
Total 
Total Band- 
Channels width 


Type 

Total 
Channels 


C> " 

Total 
Band- 
wiuth 


Grade 1 
Grade 2 
Grade 3 


(A) 60 
(B) 30 
(C) 20 


3000 me 
1500 me 
1000 me 


(D) 36 
(E) 18 
(F) 12 


1800 me 
900 me 
600 me 


(G) 18 
(H) 9 
(D 6 


900 mo 
450 me 
300 me 



Service A would appear to be the type that will eventually be 
required for a truly competitive nation-wide service. 



360 STATEMENT ON THEATER TELEVISION October 

Service E although somewhat restrictive, would serve as an interim 
measure and would be suitable for high-detail transmission. 

Service I would serve some present needs, but probably would be 
unsatisfactory and outmoded in a very short time. 

It is recommended that as many of the channels as possible be set 
aside at this time in the region of 5925 to 7125 megacycles because 
equipment is now available for use in this region, and experience with 
transmission at these frequencies shows such service to be practical. 
Although Services A and B above require more channels than this 
region can furnish, future growth may provide experience and equip- 
ment making transmission at higher frequencies also practical. 

NETWORK FACILITIES As of today, no communications organiza- 
tion, whether common carrier or limited or private carrier, is in a 
position to provide intercity or network service for theater television. 
This holds true even for transmission of 525-line pictures of present- 
day television-broadcast quality. Indeed television broadcasting 
does not presently have sufficient network facilities to avoid channel 
sharing and consequent enforced network-channel scheduling. 

The daily peak demand for network interconnection facilities for 
theater television will occur at the same time as the peak demand for 
facilities for television broadcasting. Since both services will require 
facilities between 11:00 A.M. and 12:00 MIDNIGHT, no apparent conser- 
vation can be obtained unless "both services use the same programs. 

Regardless of how many separate channels ultimately are required 
by a nation-wide theater television service, that number will remain 
the same whether distribution is by common, limited, or private 
carrier. 

Opinions as to the relative feasibilities or economies of any one 
method of distribution are not within the scope of the Society's 
interest. It does seem appropriate, however, to outline for the 
Commission some of the factors which the theater television user 
might consider in determining the operating group best suited to 
supply theater television distribution needs. 

FACTOR 1. TECHNICAL PERFORMANCE The quality of the 
provided circuits or channels to a large extent determines the qual- 
ity of the received picture. 

FACTOR 2. OPERATIONAL FLEXIBILITY Particularly in such 
fields as theater television, quick and effective responsiveness to 
program-scheduling requirements is required. 



1949 STATEMENT ON THEATER TELEVISION 361 

FACTOR 3. INTERCONNECTION AND CO-ORDINATED STAND- 
ARDS The various pickup and distribution channels, both local 
and long-distance, may require frequent, rapid, and satisfactory 
interconnection. This procedure inherently involves acceptance 
and use of co-ordinated standards of equipment performance and 
operational methods. 

FACTOR 4. AVAILABILITY As theater television operations 
expand, the correspondingly required pickup and distribution 
means should keep abreast of such expansion, or even reasonably 
precede it as a stimulating measure. 

FACTOR 5. RESPONSIVENESS TO SPECIAL NEEDS It is likely 
that theater television will have numerous special requirements 
of equipment and operation, discovered as the result of practical 
operation. The program-carrier organization should -be partic- 
ularly responsive to such needs and in a prompt and sympathetic 
fashion. 

FACTOR 6. NON ADAPTATION TO OTHER SERVICES AND USERS 
In certain cases, a group of services or number of users may come 
into conflict as to availability, or specifications, of the desired 
services. In its nature, theater television requires maximum free- 
dom from such limitations and handicaps which, in practice, might 
otherwise be insurmountable. 

FACTOR 7. PROTECTION OF PIONEERS The theater television 
organizations which either authorize facilities construction 
through a firm order for the resulting service, or which themselves 
sponsor such facilities, seem entitled to the long-term and unre- 
stricted use of such facilities. Pioneering in so complex and 
costly a field as theater television is not to be expected unless such 
reasonable protection or recognition is available. 

FACTOR 8. COST The construction and maintenance costs 
of limited or private carriers must be fully considered in compari- 
son to any proposed rental or the other costs for equivalent service 
by a common carrier. 

CONCLUSIONS The Society's answer to the six specific questions 
can be briefly summarized as follows : 

1. For a limited nation-wide theater television service, the 
minimum frequency requirements are three 50-megacycle channels 



362 STATEMENT ON THEATER TELEVISION 

for each programming source. However, for a truly competitive 
nation-wide service, each source will require from four to six 50- 
megacycle channels. If only local operation is anticipated, each 
program-originating source could operate with two 50-megacycle 
channels. 

2. As many channels as possible should be allocated for theater 
television service between 5925 megacycles and 7125 megacycles. 

3. In brief, the functions to be performed in the channels assigned 
to each program-originating organization are remote pickup, trans- 
mission from a central studio or transmitters to local theaters, and 
transmission from the central studios or transmitters in one city 
to studios, transmitters, or theaters in another city. 

4. At the present time, limited cable facilities might be made 
available for occasional transmission of low-definition monochrome 
theater television pictures, but would not be satisfactory for the type 
of theater television service considered necessary or for future high- 
detailed monochrome or color theater television pictures. 

5. As of today, no existing common carriers have facilities fully 
available for theater television purposes. 

6. The SMPE has no plans or proposals looking toward the estab- 
lishment of a theater television service. Information on this phase 
of theater television should be secured from the various motion 
picture trade associations and producer or exhibitor companies now 
carrying on experimental work. 

The Society of Motion Picture Engineers has previously submitted 
to the Federal Communications Commission proposals for the allo- 
cation of frequencies for theater television, and the Commission has 
issued statements in relation thereto. One of these was in connection 
with docket 6651 leading to the Commission's report of May 25, 
1945. The other was treated in the Commission's report of February 
20, 1948. 

The Society of Motion Picture Engineers desires to express to the 
Federal Communications Commission its willingness to be of future 
service to the Commission along such lines as the Commission may 
indicate, within the purposes and scope of the Society. 



'or table Device for 
Measuring Radiant Energy 
at the Projector Aperture* 

BY A. J. HATCH, JR. 

STRONG ELECTRIC CORPORATION, TOLEDO 2, OHIO 



Summary Studies relating to the effects of radiant energy upon the film in 
the projector aperture have become of increasing importance with the use of 
higher volumes of projected light. A portable device for measuring the 
radiant energy at the center of the projector aperture is described and its 
construction outlined. Radiant energy in units of watts per square milli- 
meter can be read directly from a self-contained indicating meter. 



INTRODUCTION 

WITH THE USE of larger theater screens, requiring a higher level of 
illumination, consideration of the limitation of total energy that 
the film can withstand has become an increasingly important factor in 
design and use of projection equipment. 

A method of evaluating the total energy at the picture aperture, 
and also the energy in various bands of the projection spectrum has 
been reported by Zavesky, Null, and Lozier. 1 The flexibility and pre- 
cision necessary for a complete evaluation of aperture energy in the 
laboratory is provided by this method, which entails the use of a wa- 
ter-cooled aperture, radiation shield, four-junction thermopile, and 
wall galvanometer. By exploring the light pattern obtained through 
a pinhole placed in the aperture plane, and integrating the readings, a 
value of total energy is obtained. 

However, many times it is desirable either to make a quick evalua- 
tion in the laboratory or to obtain measurements on actual operating 
installations in theaters. For this purpose a faster method and a 
more portable device is needed. 

One such portable instrument has been developed (Fig. 1) which 
permits a value of total center-aperture energy to be read directly 

* Presented June 10, 1949, at the Central Section Regional Meeting, Toledo, 
Ohio. 

OCTOBER, 1949 JOURNAL OF THE SMPE VOLUME 53 363 



364 



HATCH 



October 



from an indicating meter. This instrument measures 3 inches in di- 
ameter and 16Y 2 inches in length, and weighs ! 3 /4 pounds, including 
the indicating meter. It is so constructed that it can be broken down 

into two parts for carrying, and 
will fit in a 9 J /2- X 7- X 372-inch 
carrying case. 






CONSTRUCTION 

This radiant-energy measuring 
device is housed in a standard 
series II 35-mm projection lens 
barrel with a 4-inch shade tube 
added. (Fig. 2.) Tubular exten- 
sions are provided on both the 
large and small ends of the barrel. 
A pinhole aperture 0.080 inch in 
diameter is placed in the far end 
of the small-end extension of the 
lens barrel and a small aluminum 
block with a tapered hole is 
fastened to the outside of this 
pinhole aperture. The sides of 
this block are approximately 0.55 
inch square, so that the entire 
block can be inserted into the 
35-mm picture aperture to a 
point where the pinhole aperture 
will come to rest In the picture- 
aperture plane. The aluminum 
block serves as a heat baffle to 
the aperture plate, while the 
mass of the pinhole-aperture 
plate serves as an inertia element 
to prevent too high a tempera- 
ture being reached on this element, 
while the reading is being taken. 
A 10-mm diameter, 12.8-mm focal length, plano-convex lens is 
placed at a distance of approximately 0.524 inch from the pinhole 
aperture and is so adjusted to project an image of the pinhole to a 
plane 13.5 inches from the aperture. 




Fig. 1 Portable radiant-energy 
measuring device showing lens barrel 
and indicating meter. 



1949 



ENERGY AT PROJECTOR APERTURE 



365 



In this image plane, which is at the far end of the large-end lens- 
barrel extension, the receiver element of a General Electric Type DW- 
60 radiation meter is placed. This extremely small radiation meter 
combines a single-junction thermocouple and an indicating meter in a 
single unit, and is held in the lens-barrel extension in a channel with a 
detent-type lock arrangement. The lens-barrel extension fits over the 
lens-barrel shade and is adjustable lengthwise in respect to the lens- 
barrel shade. 

With nearly all motion picture arc projection systems, glass is used 
either in the form of reflectors or condensers between the arc and the 



.HEAT BAFFLE 




PROJECTION LENS BARREL 



RADIATION METER 




.RECEIVER ELEMENT 



.LARGE END 
EXTENSION 



Fig. 2 Constructional details of portable meter. 

picture aperture. Consequently, it is permissible to use a glass lens 
and a glass window for the meter receiver element, without intro- 
ducing any appreciable error in energy measurement due to selective 
response. 

DESIGN CONSTANTS 

The indicating meter scale is in units of gram calories per square 
centimeter per minute with a full-scale value of 2 units. As investiga- 
tions of aperture energy have been made in units of watts per square 
millimeter at the aperture, it was decided to select the instrument 
constants, so that the meter full scale would indicate 1 watt per square 
millimeter total energy at the aperture. As 1 gram calorie per square 



366 HATCH October 

centimeter per minute is equal to 0.449 watt per square inch, full-scale 
reading of the indicating meter is obtained when projecting 0.898 watt 
per square inch to the receiver plane (2 X 0.449). Converting 1 watt 
per square millimeter at the aperture to watts per square inch gives a 
value of 645 watts per square inch. With a lens-transmission efficiency 
of 85 per cent, the magnification constant necessary to convert 645 
watts per square inch at the aperture to a full-scale meter reading of 
0.898 watt per square inch at the receiver plane, is as follows : 



M = J 645 * - 85 =247 
\ 0.898 



CALIBRATION 



An approximately correct calibration, utilizing the design constants, 
will result, if the receiver element plane is maintained at a distance of 
I3 l /z inches from the pinhole aperture, and the distance between the 
pinhole aperture and lens varied to obtain either a sharply defined 
spot in the receiver plane, or a spot diameter 24.7 times the pinhole 
diameter. The accuracy of the receiver and millivoltmeter unit is 
==5 per cent of full scale any place on the scale, which means an ac- 
curacy of 0.05 watt per square millimeter at the aperture. 

A more accurate calibration of the over-all instrument can be made 
by adjusting the lens setting, so that the readings obtained agree with 
the laboratory method already mentioned. With the meter calibrated 
for several points against the more exact laboratory method of meas- 
uring the aperture energy, and with the application of the resulting 
correction factors, an over-all accuracy of about 2 per cent can be 
expected. 

METHOD OF USE 

To obtain a measurement of total center-aperture energy, simply 
remove the projection lens and insert the aperture-energy meter into 
the lens holder so that the aluminum block enters through the picture 
aperture. Make sure that the projector-shutter blades are out of the 
light path and prop the fire shutter open. After checking the arc 
current and the setting of the positive carbon in relation to the lamp- 
house optical system, open the lamp dowser long enough for the motor 
needle to come to a steady position. Immediately upon reading flic 
value, the dowser should be closed. The heat capacity of the pin- 
hole aperture is small, and it will become a radiator of some propor- 
tion, if subjected to the radiant energy for any but the short period 



1949 ENERGY AT PROJECTOR APERTURE 367 

that it takes for the meter hand to reach a stable position. For meas- 
urements below 1 watt per square millimeter, it will not be necessary 
to operate the projector shutter. For measurements of over 1 watt 
per square millimeter the projector shutter -can be operated, and 
the meter reading corrected for the shutter-transmission value. On 
projectors equipped with front and rear shutters, and when it is nec- 
essary to operate the shutter when taking a reading, the front shutter 
blade must be removed. 

An interesting alternate use to which some of the basic elements of 
this instrument have been put has been the measurement of the visible 
light in lumens per square millimeter at the center of the aperture. 

A measurement of this type is made by removing the radiation 
meter and substituting a photronic cell with viscor filter. By appli- 
cation of the proper calibration factors, the visible light at the aper- 
ture can be determined. 

Knowing the width of picture, projection lens, and shutter-trans- 
mission efficiency, a figure of center screen illumination in foot-candles 
can be arri ved at if desired. 

REFERENCE 

(1) R. J. Zavesky, M. R. Null, and W. W. Lozier, "Study of radiant energy at 
motion picture film aperture," J. Soc. Mot. Pict. Eng., vol. 45, pp. 102-108; 
August, 1945. 



Report of 

Lens- Calibration Subcommittee 

I. INTRODUCTION 

THIS SUBCOMMITTEE of the Standards Committee was appointed 
primarily to establish a standard method of photometrically 
calibrating diaphragm openings for motion picture camera lenses as 
distinguished from the well-known / system of aperture markings. 
The demand for a photometric type of aperture calibration ("T 
stop") is becoming increasingly felt, and it has the advantage that 
diaphragms of any shape, pentagonal, scalloped, or irregular, can be 
correctly labeled with as much ease as a circular aperture. The 
presence or absence of antireflection coatings is automatically in- 
cluded in the calibration, and so also are factory variations in the 
focal length and in the iris mechanism. The illumination on the 
film in the center of the field will therefore be the same for all lenses 
at the same T stop, assuming that the object is a uniform plane sur- 
face perpendicular to the lens axis. It is implicit, also, that each lens 
shall be individually calibrated if the photometric method is used. 

Lens speeds for distant objects only are considered in this report; 
the corresponding problem for lenses intended to be used with near 
objects will be discussed later. 

II. THEORY 

Suppose we have a well-corrected lens satisfying the sine condition, 
and used with a very distant object. Then if at some given diaphragm 
opening the area of the entrance pupil is A and the focal length is /, 
the illumination at the center of the field will be E, where 

E = tBA/f*. (1) 

In (1) t is the transmittance of the system (emerging flux divided by 
entering flux), and B is the brightness of the object in candles per 
square unit. 

For the special case of a lens having a circular aperture, 



hence E ~ 4(/ number)' (3) 

where / number is equal to l/(2 sin 0). (4) 

368 OCTOBER, 1949 JOURNAL OF THE SMPE VOLUME 53 



LENS-CALIBRATION REPORT 



369 



Equation (1) shows that for a very distant object of brightness B, 
the image illumination at the center of the field is proportional to 
tA/f 2 . For a circular aperture, (3) shows that the central image illu- 
mination is proportional to /(/ number). 2 

Note also that in (4), the sine is correct and not the tangent, because 
in a lens satisfying the sine condition the "principal plane" is actually 
a sphere centered about the focal point. 

III. DEFINITION OF / NUMBER 

The definition of /number given in (4) above is in accordance with 
American Standard Z38. 4. 20-1948, paragraph 2.5. For a lens satis- 
fying the sine condition and having a circular aperture, the / number 



r > 




_j 


L ' 


, 

) | 


s 






z 


J : 








Fig. 1 

is also equal to the ratio of the focal length to the diameter of the en- 
trance pupil, thus 

1 



/ number = : 



2 sin 6' 



(5) 



If the lens aperture is noncircular, as often happens when an iris dia- 
phragm is partly closed, the area A of the entrance pupil must be 
measured instead of its diameter D. The effective diameter D' of the 
entrance pupil will then be defined as 



lence, 



/number = 



!!_/./. 
^ 



(7) 



IV. DEFINITION OF T NUMBER 

In order to embody the lens transmittance and the area of the dia- 
iragm into a single figure which can be engraved on the lens, it is 
>posed to adopt a new term to be known as the "T number" of a 



370 LENS-CALIBRATION REPORT October 

given lens at a given opening. This T number is to be defined as the/ 
number of an open circular hole, or of a fictitious lens having 100 per 
cent transmittance and a circular aperture, which would give the 
same central-image illumination as the actual lens at the specified 
stop opening (assuming a very distant object). 
Hence, for a lens with a circular aperture, 



T number = (8) 

Vt 

and for a lens with an entrance pupil of any shape and area A, the 
corresponding formula is 



T number = s*Z.. (9) 

2 \ tA 

In practice, however, it is expected that the normal procedure will 
be to re-engrave the iris-diaphragm ring on the lens at a series of defi- 
nite T numbers, rather than to measure the T number corresponding 
to each of the existing marked /numbers. 

It may be remarked that the T number is a photometrically deter- 
mined quantity, whereas the / number is a geometrical quantity. 
Since the T numbers are determined photometrically, they automati- 
cally take account of the size and shape of the aperture, the actual focal 
length of the lens, the lens transmittance, and any internally reflected 
stray light which may happen to strike the film at the center of the 
field (such as in a flare spot). 

V. STANDARD SERIES OF APERTURE MARKINGS 

The iris-aperture ring of a lens shall be marked at every whole stop 
on either system. The diaphragm ring shall always be turned in the 
closing direction, and not in the opening direction. The whole stop 
numbers are accurately 0.71, 1.00, 1.41, 2.00, 2.83, 4.00, 5.66, 8.00, 
11.31,16.00,22.63,32.00,- 

These marks shall be engraved on the lens as follows: 0.7, 1, 1.4, 2, 
2.8, 4, 5.6, 8, 11, 16, 22, 32. The maximum aperture of the lens shall 
be marked with its measured / number or T number, stated to one 
decimal place. These recommendations follow the American Stand- 
ard Z38.4.7-1943. 

VI. SUBDIVISIONS OF A WHOLE STOP 

In addition to the engraved values, each stop may be divided into 
three subdivisions by dots or marks (not numbered), the dots being at 



1949 LENS-CALIBRATION REPORT 371 

"thirds of a stop," namely, 0.7, 0.8, 0.9, 1.0. 1.13, 1.27, 1.4, 1.6, 1.8, 
2.0, 2.2, 2.5, 0.S, 3.2, 3.6, 4-0, 4.5, 5.0, 5.0, 6.3, 7.1, 8.0, 9.0, 10.0, JJ.3, 
12.7, 14.2, 16, 18, 20, 0S, 25, 28, 32.0, - 

The reason for dividing each stop interval into three parts is so that 
the lens apertures will agree with the exposure-meter markings stated 
in American Standard Z52. 12-1944, page 5. The same cube-root-of- 
two series is used for the Exposure Index of a film, see American Stand- 
ard Z38. 2. 1-1947, page 11. One third of a stop represents a logarith- 
mic illumination ratio equal to 0.1, which is the transmission of a neu- 
tral density of 0.1. It is worth noting that \/2 is equal to tyW, or 
1.260. The ratio of successive circular stop diameters is equal to \/2 
= 1.123. 

It is contemplated that a lens will be engraved with either the / 
numbers or the T numbers, but not with both sets of markings. 

VII. SYMBOL 

Lenses calibrated on the/ system should bear the designation// or 
/: followed by the numerals (see American Standard Z38.4. 7-1943). 

Lenses calibrated on the T-stop system should bear the designation 
T or T- followed by the numerals. 

VIII. ACCURACY OF MARKING (/SYSTEM) 

The maximum opening of a lens on the / system shall be marked 
with an accuracy of 10 per cent of area, or 5 per cent of diameter.* 
Since blanket calibrations are generally used for / apertures, the 
smaller openings may be in error by 25 per cent of area, or 12 per 
cent of diameter (one third of a stop) . These figures are based on the 
assumption that the iris will always be closed down to the desired 
aperture and not opened up from a smaller aperture, to eliminate 
backlash effects. 

* In Z38.4.4-1942 the engraved focal length of lenses for still picture photography 
must be within 4 per cent of its true value, and in Z38.4.7-1943 the measured 
diameter of the maximum entering beam shall be at least 95 per cent of the quo- 
tient obtained by dividing the engraved focal length by the engraved / number. 
Thus by combining these tolerances we find that the diameter of the maximum 
lens aperture may be in error by as much as 9 per cent. This represents an error 
in area of 18 per cent, or one quarter of a stop, which is felt to be unnecessarily 
large for the maximum aperture. The proposed tolerance on aperture marking 
for motion picture objective lenses allows less latitude than that provided for still 
picture camera lenses by Sectional Committee Z38 (Photography), because of the 
stricter requirements in cinematography for uniform density of successive scenes 
photographed on the same continuous length of film using different lenses. 



372 LENS-CALIBRATION REPORT October 

IX. ACCURACY OF MARKING (T SYSTEM) 

Since each lens is individually calibrated, an accuracy of Vio of a 
stop (7 per cent in illumination) becomes entirely possible throughout 
the whole range of the diaphragm scale. This is assuming that the 
diaphragm is always closed down to the desired aperture and not 
opened up from a smaller aperture, to eliminate backlash effects. 
Alternatively, the manufacturer should be prepared to guarantee this 
accuracy even though each stop marking may not be individually 
determined. 

APPENDIX I 

X. MEASUREMENT OF / APERTURES 

The procedure for measuring the / number of any lens having a cir- 
cular diaphragm aperture is described in American Standard Z38.4.20- 
1948, paragraph 3. 

If the entrance pupil is noncircular, it is necessary to measure its 
area. Ths may be done conveniently by mounting a point source ot 
light at the rear focal point of the lens, and allowing the light beam 
which emerges from the front of the lens to fall upon a piece of photo- 
graphic material. After processing, the recorded area is measured 
with a planimeter and applied in (7) above. If the lens is too small for 
this procedure to be employed, it may be placed in a suitable projector 
working at a known magnification (a workshop profile projector 
equipped with a telecentric optical system is suitable), the back of the 
test lens being towards the source of light. The entrance pupil then 
will be projected onto the screen of the projector at a known magni- 
fication, whence its area can be determined with a planimeter. 

APPENDIX II 

XI. PHOTOMETRIC CALIBRATION OF A LENS 

Since T stops are based on a measurement of the illumination pro- 
duced by the lens at the center of the field, it is first necessary to define 
this term. 

The term "center of the field" for illumination or flux measurements 
shall be taken to mean any area within a central circle approximately 
3 mm in diameter for 35-mm or 16-mm films, or 1.5 mm in diameter for 
8-mm films. 



1949 LENS-CALIBRATION REPORT 373 

The light used in making the determination shall be white, * and the 
sensitivity characteristic of the photoelectric receiver shall approxi- 
mate that of ordinary panchromatic emulsion, t It is not considered 
that these factors are at all critical, and that no closer specification 
than this is necessary. Obviously errors will arise if the light trans- 
mitted by the lens has a strongly selective transmission, but such 
lenses would be undesirable for other reasons. 

The incident light shall fill a field not exceeding 10 degrees more 
than the angular field of the lens itself. During measurement, the 
light shall traverse the lens in the direction normally employed in pho- 
tography. The lens should be carefully examined before calibration 
to ensure that there are no shiny regions in the barrel which would 
lead to flare or unwanted stray light, since this would vitiate the meas- 
urements badly. The lens surfaces should of course be clean. 

XII. CORNER-TO-CENTER RATIO 

Having calibrated the stop markings of the lens on the T system, 
the observer may, if desired, determine in addition the ratio of corner 
illumination to center illumination, at full aperture and preferably at 
other apertures also. For this purpose the 3-mm (or IVa-mm) hole 
shall be used first at the center of the field, and then moved out- 
wards until its rim is touching the top and side limits of the camera 
gate. This distance is shown in Table I. 

TABLE I 



Gate, Mm 


Radial Shift of Hole, 


Mm 


35(16.03X22.05) 
16 ( 7.47 X 10.41) 
8( 3.51 X 4.80) 


11.5 
4.5 
2.0 





The corner-to-center ratio of illumination so determined will take care 
of cos 4 and vignetting effects within the lens. 

XIII. EXTENDED SOURCE METHOD OF T-STOP CALIBRATION 
This method of lens calibration has been described by Gardner 13 and 
Sachtleben, 9 the underlying theory being given by McRae. 4 It is based 

* Specifically a tungsten filament lamp operating between 2900 and 3200 de- 
grees Kelvin. 

t A suitable cell is one having an S-3 surface, combined with a Corning 9780 glass 
filter about 2.5 mm .thick. 



374 LENS-CALIBRATION REPORT October 

on filling the lens with light from an extended uniform source, and plac- 
ing a metal plate in the focal plane of the lens with a 3-mm hole (or 1.5- 
mm for 8-mm film) at its center. The light flux passing through 
the hole is measured by a photocell arrangement. This flux is then com- 
pared with the flux passing through the same hole from an open circu- 
lar aperture of such a size and at such a distance from the plate that 
it subtends the desired angle 6 referred to in (2) above. The greatest 
care is necessary to ensure that the extended source is really uniform. 

In practice, the photocell reading for each whole T-stop number is 
first determined for a series of open apertures, at a fixed distance from 
the plate. The lens is then substituted for the open aperture with the 
3-mm hole accurately in its focal plane, and the iris of the lens is 
closed down until the photocell meter reading produced by the lens is 
equal to each of the successive open-hole readings. The full T-stop 
positions are then marked on the diaphragm ring of the lens. The in- 
termediate third-of-a-stop positions may be found with sufficient 
accuracy by inserting a neutral density of 0.1 or 0.2 behind each open 
aperture in turn and noting the corresponding photocell readings. 

The following table of aperture diameters may be useful. They are 
based on a distance of 50 mm from aperture to plate. (It is important 
to remember the difference between sine and tangent, and that the 
aperture diameter is not found merely by dividing 50 mm by the T 
number.) 

TABLE II 

Value of 8 = Cosec -1 Diameter of 

(2 X T 7 Number), Aperture = 100 tan 0, 

Desired T Number Degrees Mm 



0.5 


90 


00 


0.71 


45 


100 


1.00 


30 


57.74 


1.41 


20.708 


37.80 


2.00 


14.478 


25.82 


2.83 


10.183 


17.96 


4.00 


7.181 


12.60 


5.66 


5.072 


8.88 


8.00 


3.583 


6.26 


11.31 


2.533 


4.42 


16.00 


1.791 


3.12 


22.63 


1.260 


2.21 


32.00 


0.895 


1.56 



1949 



LENS-CALIBRATION REPORT 



375 



A single set of apertures is sufficient to calibrate lenses of all focal 
mgths, since the only factor involved is sin 0, and that is fixed by the 

>erture used. 

The extended source should be uniformly bright over its useful area 

within 3 per cent. (This could be tested with a suitable telepho- 
teter, or a small hole in an opaque screen could be moved around 

front of the source, and any consequent variations in photocell 
reading noted.) The source conveniently may be a sheet of ground 
glass covering a hole in a white-lined box containing several lamps 
mounted around the hole and shielded so that no direct light from the 
lamps falls on the ground glass itself. The photocell receiver conveni- 
ently may be of the phototube type with a simple direct-current 
amplifier.* Care must be taken to ensure that the phototube sensi- 
tivity and the line voltage do not change between making readings on 
the open aperture and on the lens itself; to guard against this, some 
convenient turret arrangement is desirable with the lens on one side 
and the open aperture on the other so that the two may be inter- 
changed and compared immediately with each other by merely turn- 
ing the turret. 

To measure the corner-to-center illumination ratio, the lens is set 
in position and the 3-mm hole and the photocell are displaced laterally 
by the desired amount. The photocell reading is noted at axial and 
corner positions, and the corresponding light ratio found from a cali- 
bration curve of the photocell meter. 

Reference is made to the RCA patent to Sachtleben, 9 U. S. 2,419,- 
421, claim 3 of which covers this method of lens calibration. 

XIV. COLLIMATED SOURCE METHOD OF LENS CALIBRATION 

This method has been described by Daily 11 and Townsley, 14 the 
underlying theory being embodied in (1) above. Light from a small 
source (a 5-mm hole covered with opal glass and strongly illuminated 
from behind) is collimated by a simple lens, or an achromat if pre- 
ferred, of about 15 inches focal length and 2 inches aperture. This 
gives a collimated beam which will be focused by the test lens to form 
a small circle of light in its focal plane. This circle of light wiJl be less 
than the prescribed limit of 3 mm diameter for all lenses under 9 
* Suitable systems are the "Electronic Photometer" model 500, (Photovolt 
Corporation, 95 Madison Avenue, New York, New York), and the "Magnephot" 
(W. M. Welch Scientific Co., 1515 Sedgwick St., Chicago, Illinois). 

It is felt that a barrier-layer cell, although desirable for reasons of simplicity, 
has insufficient sensitivity for accurate determinations of the smaller apertures. 



376 LENS-CALIBRATION REPORT October 

inches in focal length. Uniformity of the collimated beam can be 
checked by moving a small hole in an opaque screen across the beam, 
and any variations in the photocell reading noted. 

For the comparison unit, an open aperture is used, of diameter 
equal to the focal length of the lens divided by the desired T number. 
This aperture is first mounted in front of an integrating sphere with 
the usual photocell detector, and the light from the collimator is al- 
lowed to enter the aperture. The aperture plate is now replaced by 
the lens, the iris diaphragm is closed down to give the same photocell 
reading, and the T-stop number is engraved on the iris ring. The in- 
termediate thirds of stops can be added by using 0.1 or 0.2 density fil- 
ters as in the method of Section Xlil. 

To guard against drift and line-voltage variations \vhich might oc- 
cur between the readings on the comparison aperture and on the lens, 
it is convenient to leave the known standard aperture in place in front 
of the sphere, and to insert the lens into the beam in such a position 
that the little image of the source falls wholly within the standard 
aperture. The meter reading should then remain the same no matter 
whether the lens is in or out of the beam. A second plate with a 3-mm 
aperture should be placed over the comparison aperture while the 
lens is in place to stop any stray light which may be reflected from the 
interior of the lens. 

It should be noted particularly that if this method is used, the focal 
length of the lens must be measured separately, and a suitable set of 
open apertures constructed for use with it. However, by suitable de- 
vices, one single set of fixed apertures may be used for all lenses, as 
described by Townsley. 14 

The corner-to-center ratio at any desired aperture can be conven- 
iently determined by simply rotating the lens through the desired field 
angle < and comparing the photocell reading with its value for the 
lens axis. The light-flux ratio can then be read off a calibration curve 
for the photocell system, and converted to the desired corner-to-center 
illumination ratio by multiplying it by cos 3 <. (Note that this pro- 
cedure will be correct only in the absence of distortion, but no motion 
picture lens is likely to have enough distortion to cause any significant 
error.) 

APPENDIX III 
XV. USE OF T STOPS WITH EXPOSURE METERS AND GUIDES 

Existing exposure meters, and all qualitative exposure guides, are 
based on the transmittance of an average uncoated lens, 17 say 76 



1949 LENS-CALIBRATION REPORT 377 

per cent. Thus existing exposure-meter dials are necessarily incorrect 
for all lenses differing in transmittance from 76 per cent. 

By using photometrically calibrated T stops in place of the purely 
geometrical /stops, the meter exposure will be in error by about 30 per 
cent, which is close to one third of a stop or one division on the dial. 
However, as the error resulting from the use of T stops instead of / 
stops is in the direction of overexposure, it is felt that no changes or 
corrections in exposure-meter dials will be necessary. 

In this connection it is of interest to note that the exposure formula 
given in American Standard Z52.22-1944, namely, 

1.25 (/number) 2 

exposure time = , , 7-. : \ 

brightness (in cdls per sq ft) X exposure index 

could be simplified for T numbers, as follows : 

(T number) 2 

exposure time = ; , : ; 

brightness X exposure index 

XVI. DEPTH OF FIELD 

It is the opinion of the subcommittee that either / stops or T stops 
may be used interchangeably for the computation of depth of field. 
This is because computed depth values are at best approximations, 
depending on an arbitrary value for the permissible circle of confusion 
in the image. Since the aperture diameter at any given T number is 
generally larger than the aperture diameter at the same/ number, the 
actual depth of field at a given stop number will be slightly less on the 
T system than on the /system. 

LENS-CALIBRATION SUBCOMMITTEE 

RUDOLF KINGSLAKE, Chairman A. J. JANSSEN 

Eastman Kodak Company . Mitchell Camera Corporation 

F. G. BACK G. LAUBE 

Research and Development Labora- Twentieth Century-Fox Film Cor- 

tories poration 

EMMANUEL BERLANT E R LEVINSON 

Berlant Associates Warner Brothers Pictures 
J. W. BOYLE 

T-, T ^. J. A. MAURER 

f ree- Lance Cinematographer 

L. E. CLARK J " A " Maurer ' Inc " 

Technicolor Motion Picture Corpora- ^- ^- MURRAY 

tj on Bausch and Lomb Optical Company 

C. R. DAILY M. G. TOWNSLEY 

Paramount Pictures Bel1 and Howell Company 

I. C. GARDNER G. C. WHITAKER 

National Bureau of Standards Graflex, Inc. 



378 LENS-CALIBRATION REPORT 

BIBLIOGRAPHY 

General 

(1) A. C. Hardy, "The distribution of light in optical systems," J. Frank. 
Inst., vol. 208, pp. 773-791; December, 1929. 

(2) A. C. Hardy and F. Perrin, "Principles of Optics," McGraw-Hill Book 
Company, New York, New York, 1932, p. 411. 

(3) L. C. Martin, "Applied Optics," vol. 2, Pitman, London, 1932, p. 210. 

(4) D. B. McRae, "The measurement of transmission and contrast in optical 
instruments," /. Opt. Soc. Amer., vol. 33, pp. 229-243; April, 1943. 

Lens Calibration 

(5) G. W. Moffitt, "Determining photographic absorption of lenses," J. Opt. 
Soc. Amer., vol. 4, pp. 83-90; May, 1920. 

(6) J. Hrdlicka, "Measuring the effective illumination of photographic ob- 
jects," J. Soc. Mot. Pict. Eng., vol. 14, pp. 531-533; May, 1930. 

(7) D. B. Clark and G. Laube, "Twentieth Century camera and accessories," 
J. Soc. Mot. Pict. Eng., vol. 36, pp. 50-64; January, 1941; also U. S. Patent 2,334,- 
906 (filed September, 1940, issued November, 1943). 

(8) E. W. Silvertooth, "Stop calibration of photographic objectives," /. Soc. 
Mot. Pict. Eng., vol. 39, pp. 119-122; August, 1942. 

(9) L. T. Sachtleben, "Method of calibrating lenses," U. S. Patent 2,419,421 
(filed May, 1944, issued April, 1947). 

(10) E. Berlant, "A system of lens stop calibration by transmission," /. Soc. 
Mot. Pict. Eng., vol. 46, pp. 17-25; January, 1946. 

(11) C. R. Daily, "A lens calibrating system," J. Soc. Mot. Pict. Eng., vol. 46, 
pp. 343-356; May, 1946. 

(12) A. E. Murray, "The photometric calibration of lens apertures," J. Soc. 
Mot. Pict. Eng., vol. 47, pp. 142-151 ; August, 1946. 

(13) I. C. Gardner, "Compensation of the aperture ratio markings of a photo- 
graphic lens for absorption, reflection, and vignetting losses," J. Soc. Mot. Pict. 
Eng., vol. 49, pp. 96-110; August, 1947; also J. Res. Nat. Bur. Stand., vol. 38, pp. 
643-650; June, 1947. 

(14) M. G. Townsley, "An instrument for photometric calibration of lens iris 
scales," J. Soc. Mot. Pict. Eng., vol. 49, pp. 111-122; August, 1947. 

(15) F. G. Back, "A simplified method for the precision calibration of effective 
/stops," J. Soc. Mot. Pict. Eng., vol. 49, pp. 122-130; August, 1947. 

(16) F. E. Washer, "Errors in calibrations of the /number," J. Soc. Mot. Pict. 
Eng., vol. 51, pp. 242-260; September, 1948. 

(17) W. N. Goodwin, Jr., "The photronic photographic exposure meter," /. 
Soc. Mot. Pict. Eng., vol. 20, pp. 95-118; February, 1933. 



Precision Lens-Testing 
and Copying Camera* 

BY M. W. LA RUE 

BELL AND HOWELL COMPANY, CHICAGO 45, ILLINOIS 



Summary The camera to be described was designed expressly for lens- 
testing and precise copy work. Its rigidity, method of photographic plate 
location, and focusing accuracy are such that it fully utilizes the capabilities 
of the high-definition lenses and photographic plates used with it. Its general 
construction is sturdy, and it has been demonstrated, by four years of con- 
tinuous use, that little or no maintenance or repair will be required for many 
years to come. 



D 



INTRODUCTION 

URING THE WAR it became necessary for Bell and Howell to make 
photographic reductions of unusual accuracy and sharpness. 
At this same time, it was being found desirable to improve on the lens- 
testing camera then being used. It was thus decided to design and 
make a camera for both lens testing and copying. The resulting cam- 
era satisfactorily accomplishes both of these functions, and it is be- 
lieved to have combined several desirable features which are worthy 
of description. 

CAMERA REQUIREMENTS 

The photographic reductions which were to be made often de- 
manded accuracy of size to tolerances of plus or minus one ten thou- 
sandth of an inch and sharply defined lines as narrow as four ten thou- 
sandths of an inch. In order to obtain such accuracy, the following 
three requirements are essential: (1) the camera must be rigid; (2) 
the photographic plates must be consistently and identically located ; 
and (3) there must be provision for accurately measurable camera fo- 
cusing. These requirements are equally essential in a lens-testing 
camera. 

Rigidity Rigidity avoids the possibility of camera movement dur- 
ing the relatively long exposures used in this type of work. Even in a 

* Presented June 10, 1949, at the Central Section Regional Meeting, Toledo, 
Ohio. 

OCTOBER, 1949 JOURNAL OP THE SMPE VOLUME 53 379 



380 LA RUE October 

reinforced concrete building with no heavy machinery, it was found 
that there was sufficient vibration to reduce picture definition notice- 
ably when using a commercial plate camera. 

Plate Location It was necessary to be able to examine the image 
visually, and then to obtain that identical image on as many photo- 
graphic plates as desired. Commercial plateholders are normally 
made of wood, and it is seldom that two plateholders will locate a 
plate in exactly the same position. Even the same plateholder cannot 
be relied upon for consistency of location. As a result, even though we 
intended to use standard plateholders to carry the plates, the plates 
had to be directly located by the camera. 




Fig. 1 Camera, front view. 

Focusing Another effect which is normally difficult to overcome is 
that the photographic focus and the visual focus of a lens are often dif- 
ferent by as much as five or six thousandths of an inch. The reason 
for this difference is that the focal point of a lens varies somewhat with 
light wavelength. The high-resolution photographic plates used in 
this type of work are sensitive to wavelengths different from those of 
the eye, making the position of best focus for the plate different than 
is indicated when focusing visually. This focus shift of a lens can be 
closely measured, and can thus be compensated for by first focusing 
visually and then accurately moving the plate or lens through the 
known distance required to bring it into photographic focus. To be 



1949 COPYING CAMERA 381 

able to do this, it was necessary to provide means for accurately 
measured movement of both the lens support and camera back. 

In addition to these three basic requirements of rigidity, direct lo- 
cation of the photographic plate by the camera, and accurate move- 
ment of both the front and back of the camera, several other features, 
though not required, were found to be desirable. These features in- 
cluded a single focusing knob for both the front and back of the cam- 
era, backlash-free focusing, means for locking both the front and back 
of the camera, and daylight loading. 




Fig. 2 Camera, rear view. 

DESCRIPTION 

It was realized, of course, that a camera such as this could not at the 
same time be made easily portable, and though every attempt was 
made to make it convenient for use, weight was not a primary consid- 
eration. Cast iron was thus used for the camera body and frame be- 
cause of its desirable vibration-damping characteristics. In spite of 
this, the final weight of 53 pounds is quite reasonable. The camera 
uses standard 4X5 plates in standard plateholders, or in a special 
plateholder (described later) when the full extent of camera accuracy 
is desired. It would be possible to accommodate smaller sizes of 
plateholders with specially designed adapters. 

The camera (Fig. 1) is adapted to fit the Bell and Howell standard 
optical bench which consists of two P/Vinch diameter rods at a center 






382 



LA RUE 



October 



distance of 8 inches. The camera base, lens support, and the upper 
and lower parts of the camera back are all iron castings. The lens sup- 
port and camera-back castings slide independently on a steel dovetail 
which is mounted on the camera-base casting. These castings are 
fitted to the dovetail in the same manner as the cross-slide on a lathe, 
with the exception that the center adjustment screw and nut on each 
have been replaced by a thumbscrew. The thumbscrews are used to 
lock either the lens support or camera back in place when desired. 
The cast construction, together with the locking provision, contrib- 
utes the utmost toward camera rigidity. 



LENS 
SUPPORT 



CAMERA 
BACK 




Fig. 3 Focusing mechanism. 

At the rear of the camera (Fig. 2), convenient to the photographer, 
is the focusing knob. This knob is calibrated in thousandths of an 
inch, and moves either the lens support or camera back, whichever is 
desired. If the camera back is to be moved, the rear thumbscrew is 
loosened and the front thumbscrew tightened. The focusing knob 
then moves only the camera back. Loosening the lens support and 
tightening the back moves only the lens support. 

Direct location of the photographic plate by the camera is accom- 
plished by lightly holding it against six locating buttons in the camera 
while the exposure is being made. Since daj^light loading was a con- 
venient feature, it was necessary to be able to replace the dark slide 
of the plateholder before removing the placeholder from the camera. 
The plate, however, first had to be retracted from the locating buttons 






1949 COPYING CAMERA 383 

to allow the dark slide to enter the plateholder. This was accom- 
plished by a cam-actuated plateholder mounting. The loaded plate- 
holder is placed in this mounting and the dark slide removed. The 
cams, which are operated by external levers, are then rotated to bring 
the plateholder toward the lens until the plate contacts the locating 
buttons. When the exposure is completed, the cams retract the 
mount, the dark slide is replaced, and the exposed plateholder may 
then be removed. There is no danger of fogging the plate, since the 
camera back is lighttight throughout the entire operation. In order 
to prevent damage to the camera-locating buttons, ;when the plate- 
holder is in shooting position the cam levers prevent removal or re- 
placement of the dark slide. 




Fig. 4 Special plateholder. 

The focusing adjustment (Fig. 3) is entirely free of backlash. The 
method by which backlash is eliminated is shown in the figure. The 
focusing knob shaft passes through a tab on the camera-back casting 
and is threaded into a tab on the lens-support casting. A collar on the 
shaft is held tightly against the camera-back tab on a small plate 
backed by two compression springs. The springs are retained in place 
by screws which are threaded into the tab and pass through clearance 
holes in the plate. This prevents the plate from turning with the 
shaft, and the screws serve also as adjustments for spring tension. 
Backlash is eliminated in the threaded end of the shaft in a similar 
manner, except that here the plate is threaded to the shaft. The pro- 
vision for movement of both the lens support and camera back by 
means of a single backlash-free calibrated focusing knob completes the 
requirements of this precision camera. 



384 



LA RUE 



October 



A total relative movement between the lens support and camera 
back of l J /2 inches can be obtained with the focusing knob. (See 
Fig. 1.) Throughout this range of movement the camera is kept 
lighttight by interfiling metal baffles on the lens support and camera 
back. This eliminates the need for a relatively fragile cloth bellows. 
Additional separation between the lens and plate, when required for 
various focal lengths, is obtained by adapters and spacers which screw 
into the lens support. By the use of these adapters and spacers, a 
lens back focus (distance from lens seat to lens focal plane) of up to 
18 inches can be accommodated. 




Fig. 5 Method of camera focusing. 

After the camera had been made it was found that the photographic 
plates used were not sufficiently flat to take advantage of the accuracy 
which had been built into the camera. It was found that, in every 
case, the plates were warped so that they were concave toward the 
emulsion side of the plate, though any one plate was always very uni- 
form in thickness. This difficulty was overcome by the use of a spe- 
cial plateholder in which a metal backing surface flattens the plate 
against the camera-locating buttons. (See Fig. 4.) 

METHOD OF USE 

Photographic Copying When the camera, is used for photographic 
reduction, the camera-to-target and lens-to-plate distances are com- 
puted approximately. With the camera at the computed distance, an 
open-backed plateholder containing a clear-glass plate is inserted in 



1949 



COPYING CAMERA 



385 



the camera. (See Fig. 5.) A microscope, placed behind the camera 
on the same optical bench, is then focused on what corresponds to the 
emulsion side of the plate. The camera front is then adjusted until 
the image of the target is also brought into focus. This focuses the 
target image on the front surface of the plate. The microscope, which is 
mounted on a micrometer cross-slide, allows the image to be examined 
and its size measured. Minor adjustments are then made with the 

4 

> -4 

.002 
005- 
010 o 
0200 




040 



050 



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T 

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Fig. 6 Photoengraving master. 

focusing knob to obtain the image size to the desired accuracy. When 
size and focus are satisfactory, the dummy plateholder is removed and 
the loaded plateholder is inserted in the camera. The dark slide is re- 
moved, and the plate brought into contact with the locating buttons 
by rotating the cam levers. The front surface of the plate is then in 
the same position as the clear-glass plate used for focusing the camera. 
At this point the correction for the difference between visual focus and 
photographic focus is made by movement of the camera back. The 
exposure is then made, the plateholder retracted, and the dark slide 



386 



LA RUE 



October 



replaced. Any number of additional plates can be exposed at this 
same camera setting with the assurance that the results will be identical. 
As an example of the type of work which is accomplished in this 
manner, Fig. 6 shows a photographic master which is used for photo- 
engraving a Bell and Howell magnifier reticle. The reticles made 

from this master are mounted at 
the focus of a well-corrected mag- 
nifier. (Fig. 7.) The combina- 
tion of reticle and magnifier is 
used for checking tool-bit angles, 
size of bubbles and flaws in opti- 
cal elements, and accurate length 
measurements. 

Lens Testing When the camera 
is used for lens testing, the method 
of setting up the camera and lens 
combination is the same. The 
target, however, consists of a 
series of resolution charts, and 
several exposures are made while 
progressively moving the plate 
position through the plane of best 
focus of the lens. When desired, 
this series of exposures can be 
used to construct a contour map 
of the photographic image. Lens 
aberrations such as spherical 
aberration, astigmatism, and 
curvature of field may thus be accurately measured. Such a pro- 
cedure is invaluable in evaluating lens quality and confirming the 
computations on a new lens design. 

As an example of what is accomplished by this type of lens-testing 
procedure an enlargement of one resolution chart, at a considerable 
angle from the optical axis, is shown in the series of Figs. 8 A to 8E. 
The exposures are spaced two thousandths of an inch apart, with the 
plates approaching and then passing through the position of best 
focus. This series of figures clearly shows the difference in focus be- 
tween radial and tangential lines caused by astigmatism. Prints of 
such a series of exposures form a permanent record of lens performance 
which may be evaluated at any time without the presence of either 
lens, microscope, or optical bench. 




Fig. 7 Bell and Howell pocket com- 
parator. 



1949 



COPYING CAMERA 



387 




Fig. 8A 




Fig. 8B 




Fig. 8C Resolution test plates. 



388 



LA RUE 




Fig. 8D 




Fig. 8E Resolution test plates. 



35-Mm and 16-Mm Sound-on-Film 
Reproducing Characteristic* 

BY JOHN K. MILLIARD 

ALTEC LANSING CORPORATION, HOLLYWOOD 38, CALIFORNIA 



Summary This paper reviews the activities and procedures used in the 
formation of the present 35-mm Motion Picture Research Council theater 
sound-equipment recommendations. Using this experience as a reference 
point, a 16-mm sound electrical characteristic is recommended. It is spec- 
ified that in both 35-mm and 16-mm fields these recommendations apply 
only to a specific type of loudspeaker and individual response curves must be 
recommended depending on the type of loudspeaker used. 



DURING THE SMPE Semiannual Convention in Washington, D. C., 
in October, 1948, an informal discussion and demonstration was 
held to compile information that could be used in arriving at standards 
for 16-mm sound-on-film reproduction. Again at the Spring Con- 
vention in New York in April, 1949, a symposium Avas held to continue 
the discussion and to have demonstrations on a variety of prints 
and reproducing equipment. 

The wide interest in standardizing 16-mm sound equipment would 
indicate the desirability of reviewing the activities which led up to the 
adoption of the 35-mm standard reproducing characteristic which 
has been very effective during the past twelve years. 

There are many factors in the recording of sound for motion pic- 
tures which cause large variations in quality on the original recording. 
Some of these points will be briefly mentioned : 

(1) The acoustic conditions in the various stages and out-of-doors 
vary over wide limits as regards absorption and reverberation. 

(2) Restrictions are imposed by set designers, lighting effects, 
and camera angles which require compromise as compared to having 
the optimum microphone placement in all cases. Some sets have 

* Originally presented October 27, 1948, at the SMPE Convention in Wash- 
ington; revised later following the 65th Semiannual Convention in New York, 
- April, 1949. 

OCTOBER, 1949 JOURNAL OF THE SMPE VOLUME 53 389 



390 HILLIARD October 

three walls, some have low ceilings, and very often one camera shot 
on the same scene will be made with a portion or all of the ceiling 
or wall removed in order to obtain the desired camera angle and/or 
lighting effect. In cases of exterior shots, the reverberation is 
extremely low and this is accompanied by a lack of both low and 
extremely high frequencies. These direct cuts from indoors to out- 
doors and back again are made at a pace which is faster than that 
encountered in real life. As a result, the individual scenes must be 
equalized so as to be more uniform in frequency characteristic. 

(3) The various studios use different types of microphones depend- 
ing upon the degree of directivity required to overcome set noise such 
as arc-light interference, wind machines, stage ventilators, and me- 
chanical noise generated by props. These microphones have a consider- 
able difference in response both in the low- and high-frequency ranges, 
and beam effects caused by changes in directivity require equalization 
in order to maintain uniform quality. 

(4) The studio endeavors to do the best possible work on the 
original recording with a minimum of delays to the production, trust- 
ing that all these variations can be taken into consideration at the 
time of re-recording for release. 

(5) Loye and Morgan 1 have pointed out the necessity of providing 
effort equalization to compensate for the fact that the speech is 
reproduced at a higher intensity in the theater than that which oc- 
curred at the time of recording. The typical studio re-recording con- 
sole is equipped with variable low- and high-pass filters and a very 
effective set of midrange equalizers, capable of producing a proper 
subjective effect to the theater audience. It is not unusual to en- 
counter variations in equalizer settings which approach a 25-decibel 
range on the low end in the neighborhood of 100 cycles and up to 
a 10-decibel change in the so-called "presence" region around 3000 
cycles. 

When all of these factors are taken into consideration, it is under- 
standable that it is not practical to assign a recording characteristic 
in detail because of the many variables which occur during the proc- 
ess of recording and re-recording for release. 

The following steps are recommended as a procedure for standardi- 
zation in both studios and theaters: 

(1) Derive the reproducing characteristic required to reduce the 
fundamental deficiencies of the medium such as noise and distortion. 



1949 



REPRODUCING CHARACTERISTIC 



391 



(2) Install, adjust, and maintain theater-type reproducing equip- 
ment in the studio review rooms which have the optimum required 
reproducing characteristic. 

(3) Adjust release film so as to have the required balanced fre- 
quency response and volume range required for theaters. 

(4) Adjust equipment in all theaters so that it gives identical 
performance in so far as possible with that in the master review rooms 
in the studios. (This implies a definite frequency response, depend- 
ing upon the exact type of loudspeaker used.) 

(5) Maintain proper correlation between those responsible for 
studio and theater standards. 

(6) Provide necessary test films which are considered standard and 
essential. 

The first co-ordinated work in leading up to the adoption of a pub- 
lished theater reproducing characteristic for 35-mm film was started 



REQUENCY IN CYCLES PES SECOND 



Fig. 1 Typical 35-mm Research Council recommended 
response curve. 



in 1937. These standard electrical characteristics were arrived at by 
conducting listening tests in several theaters with the object in mind 
to obtain the most suitable characteristic which would suitably 
reproduce all of the current studio product then available. In arriv- 
ing at this standard electrical characteristic, several fundamental 
factors had to be taken into consideration. It was recognized that 
the background noise on film made it necessary to use a characteristic 
favoring the reduction of this noise. This required that a certain 
amount of roll-off or droop in the high-frequency spectrum be used. 
This factor was evaluated by observing the characteristic required 
to reproduce unmodulated film with a gain setting which is normally 
encountered while running a picture. Having determined this 



392 . HILLIARD October 

characteristic, it was then necessary to analyze the recording char- 
acteristic and verify that this reciprocal amount of pre-equalization 
could be used. An example of a typical response curve recommended 
by the Motion Picture Research Council for 35-mm work is shown in 
Fig. 1. This response applies only to a specific type of loudspeaker. 2 

In order to make available adequate acoustic power it is necessary 
to determine the efficiency of the various loudspeakers. A typical 
curve showing the recommended power for a given number of seats 
has been published by the Research Council. This recommendation 
assumes a loudspeaker efficiency of approximately 25 to 35 per cent 
over-all. 

Limitations in the region below 100 cycles are required because of 
the presence of noise reduction or shutter bumps. The timing con- 
stant of the noise-reduction equipment is such that this occurs below 
50 cycles. It is the author's opinion that an ideal theater reproduc- 
tion should include a high-pass filter which begins to cut off at 45 or 50 
cycles. This would allow maintaining the characteristic more nearly 
flat down to cutoff. 

By reviewing the procedure for creating the 35-mm standard, it 
should clarify the ideas considered necessary to formulate the 16-mm 
standard reproducing characteristic. A large amount of 16-mm out- 
put is derived from original 35-mm film. The general standard for 
film-laboratory development equipment in present 16-mm release 
has been lower than that for the 35-mm field. This undoubtedly 
has been influenced by the cost to the user. Recording characteristics 
have been largely influenced by high rates of flutter, wow, low ampli- 
fier capacity, low efficiency, and poor response of loudspeakers. The 
loudspeakers have been of the inexpensive type and usually small 
portable cabinets are used. 

In Fig. 2 the solid line shows the response that has been used for 
many years in the re-recording channels to minimize the above de- 
ficiencies. The dotted curve is the re-recording channel curve that is 
now being considered for extensive use. These curves have been 
arrived at on the basis of listening to loudspeakers designed for 35-mm 
work and by taking into consideration the defects which have been 
present in 16-mm. These curves are re-recording curves only and 
should not be misconstrued as a recording characteristic. 

Recently, demonstrations have been held which indicate that equip- 
ment is now, or will shortly be, made available, which removes many 
of the objections mentioned. Improved printers, direct positives, 



1949 



REPRODUCING CHARACTERISTIC 



393 



and, 16-mm projectors incorporating 35-mm features demonstrate 
that much better 16-mm work will be done in the future. Optical 
slits, giving an effective scanning height of 0.6 to 0.7 of a mil, are now 
being employed. This means that response can be obtained up to 
5000 cycles without excessive equalization. It seems logical and 
practical to have the electrical characteristic for 16-mm reproduction 
follow very closely that of 35-mm up to 5000 cycles. Low-pass filters 
can then be installed at 5000 or 6000 cycles, depending upon the 
nature of the material and application. As was considered on the 
35-mm characteristic, the loudspeaker system must be taken into 
consideration when evaluating the final reproduction curve. 













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FREQUENCY IN CYCLES PER SECOND 



Fig. 2 Approximate re-recording characteristics; 35-mm 
release sound track for 16-mm release. 



Fig. 3 shows the recommended optimum response which is easily 
obtained with simple networks, and the dotted line shows the ideal 
characteristic that is desirable. In portable equipment it naturally 
follows that the characteristic must be balanced around a geometric 
mean 3 of 800 cycles. It is not advisable to extend the high-frequency 
end when the loudspeaker enclosure will not maintain a balance at the 
low end. Where larger two-way systems are to be used, and are the 
equivalent of that being used in 35-mm, the over-all characteristic 
can approximate the 35-mm characteristic over a range of approxi- 
mately 80 to 6000 cycles. 

The Navy has recently indicated that all of their future planning 
for mobile or portable motion picture presentation will use only 16- 
mm release. As a result of this large single user, it seems desirable 



394 



HlLLIARD 



October 



to have a committee of the Society of Motion Picture Engineers pro- 
vide a recommended curve in the same manner that the 35-mm field 
has already been standardized. 

In closing it is recommended that the following steps be taken to 
standardize 16-mm sound-on-film reproduction. 

(1) Use a reproducing characteristic which is similar to the 35-mm 
characteristic except for minor deviations on the very low- and high- 
frequency bands. 

(2) Provide recommended reproducer characteristics which will 
vary depending upon the type of loudspeaker used. 

(3) Publish information about currently available test films in 
order to accomplish this standardization. 



' ' RE'COMMENDED'OPTI 
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100 2C 


10 500 


1000 2000 5000 


0000 



FREQUENCY IN CYCLES PER SECOND 



Fig. 3 16-mm electrical response for 2- way theater loud- 
speakers. 



(4) Establish a responsible group to correlate recording and 
reproducing activities so that standards may be modified when the 
art permits. 

This material has been presented in the hope that a discussion of 
the principles involved will enable workers in the field to arrive at an 
agreement which will promote higher standards of quality in the 16- 
mm field. 

NOTE: Since this paper was presented, the Society of Motion 
Picture Engineers 16-Mm Sound Reproduction Subcommittee April 
7, 1949, Report unanimously agreed to accept the electrical charac- 
teristics recommended in Fig. 3 solid line. 



1949 REPRODUCING CHARACTERISTIC 395 

REFERENCES 

(1) D. P. Loye and K. F. Morgan, "Sound picture recording and reproducing 
characteristics/' /. Soc. Mot. Pict. Eng., vol. 32, pp. 631-648; June, 1939; vol. 33, 
p. 107; July, 1939. 

(2) Motion Picture Research Council, Inc., Technical Bulletin, "Standard Elec- 
trical Characteristics for Theater Sound System," April 20, 1948. 

(3) "Motion Picture Sound Engineering," D. Van Nostrand, New York, New 
York, p. 100, 1938. 

DISCUSSION 

MR. J. A. MAURER: Mr. Hilliard, how would a projector manufacturer go 
about measuring the equipment to determine that he has the response recom- 
mended. 

MR. J. K. HILLIARD: The Society of Motion Picture Engineers has test films 
which are calibrated on the basis of what you might call constant modulation and 
certainly by placing those in the projector and measuring, you ought to be able to 
determine the performance conditions in so far as frequency response occurs. 
Other types of tests as used in the 35-mm field are also available for 16. 

MR. MAURER: I wanted to make sure that you did intend those curves to be 
expressed in terms of the standard test films. 

MR. J. K. HILLIARD: Yes. It should have been indicated on the slide that 
they were in terms of constant modulated films. 

MR. ELLIS W. D'ARCY: Is there anything proposed to tighten up conditions 
with respect to quality and things like that? Is there to be a standard established 
at this time in that respect as well as frequency-wise? 

MR. J. K. HILLIARD : Certainly we cannot extend the frequency range without 
improving the other techniques which are admittedly deficient up to this time. 
As you all know, such things as flutter and distortion have contributed to keeping 
the range as limited as it is now -and we hope by co-ordinating the work of all 
those interested, from the manufacture of the film down to the final release in the 
theater, to get these people together on a common understanding as to where 
the bottlenecks now exist and, if possible, open up those to a point where the 
present handicaps will not be maintained. 



Desirable Locations for 
Theater Sites* 

BY E. G. FALUDI 

PLANNING CONSULTANT, TORONTO, ONTARIO, CANADA 



Summary Land economics, sociology, and physical planning have en- 
abled us to determine with scientific exactness the characteristics of the 
urban retail structure, of which the theater is a part. Today, the selection 
of the location of the theater is more important than ever before because of 
various new trends adversely affecting the motion picture industry. The 
following is the basic information required to determine the suitability of a 
location and site for a theater: size of the tributary population; living and 
spending habits; the retail pattern; physical characteristics; and the antic- 
ipated development of the area. Once these factors are ascertained, we 
can determine the relation between seating capacity and population hi the 
tributary area and evaluate the economics involved. 

f~\ VER THE PERIOD of half a century, the motion picture industry has 
V>J grown to one of the five largest industries in the United States. 
This achievement is partly because of the leadership of a pioneer 
generation which had the business acumen to foresee the possibilities 
inherent in the motion picture and which had the capacity to develop 
and industrialize it. For the last ten years, however, social and 
economic trends, new technological inventions, and developments 
within urban and rural areas have been endangering the privileged 
position of this industry. 

What the direct effect of these trends and changes will be on the 
industry as a whole is difficult to forecast, since no over-all survey 
has been undertaken covering each of its fields or branches. 

However, sufficient data and information are available to define the 
anticipated effects on the motion picture theater and to establish the 
conditions under which it may operate and serve a community most 
successfully. 

TREND IN SOCIAL ACTIVITIES AND THE MOTION PICTURE THEATER 

The importance of the trend in social activities as related to the 
motion picture theater is revealed by recent surveys conducted on the 



* Presented April 8, 1949, at the SMPE Convention in New York. 
396 OCTOBER, 1949 JOURNAL OF THE SMPE VOLDME 53 






THEATER SITES 



397 



North American continent and in five European countries. In one 
of these surveys the question was asked " Would you mind telling me 
which, if any, of the following you did last night?" The person inter- 
viewed gave his answer from the list of activities and the answers 
\vere compared, as shown in Table I. 

TABLE I 
SURVEY OF SOCIAL ACTIVITIES 





U.S.A. 














and 














Canada 


Denmark 


Holland 


Sweden 


Norway 


France 








-pj 


tage 


x 




"i ercen 


Read 


19 


23 


17 


21 


21 


21 


Listened to radio 


28 


13 


18 


22 


18 


22 


Entertained or was 














entertained 


17 


16 


18 


19 


6 


12 


Played cards 


10 


6 


6 


2 


4 


1 


Went to motion pic- 














tures or theater 


7 


4 


7 


4 


5 


7 


Watched sports 


4 




1 








Danced 


2 




1 




1 


1 


Other 


13 


38 


32 


32 


45 


36 




100 


100 


100 


100 


100 


100 



This survey indicates that in the United States and Canada, as a 
form of commercial entertainment the radio attracts four times as 
many people as motion pictures. (See Fig. 1.) The high percentage 
of radio listeners in relation to those who go to motion pictures is 
chiefly because the former offers free entertainment. In the field 
of paid entertainment the closest competition is the sport show which 
attracts 4 per cent as compared with the 7 per cent attracted by the 
motion picture. 

TREND IN SOCIAL HABITS AS RELATED TO THE MOTION PICTURE 

THEATER 

The most recent indication of the impact which television is having 
on social habits is contained in a survey conducted by the Duane 
Jones Company among television-set owners in the metropolitan 
area of New York. A questionnaire was mailed out in mid-November 
to 4500 television-set owners, and the results are based on a 35 per cent 
response. 



398 



FALUDI 



October 



Of those answering the poll, 92.4 per cent said that they now listened 
less to the radio, 80.9 per cent see fewer motion pictures, 58.9 per cent 
read books less, 48.5 per cent read magazines less, and 23.9 per cent 
read newspapers less. 

On the other side of the ledger, 72.1 per cent reported that more 
children visited their homes on social visits and 76.8 per cent said that 
their adult entertainment had increased. 

THE THEATER AND POPULATION 

In order to evaluate these data with reference to anticipated 
theater attendance, we shall consider first the potentiality of the the- 
ater in relation to population figures. 




Fig. 1 Social activities in the United 
States and Canada. 

In the large urban centers of Canada and the United States, there 
is a theater seat provided for every 7 to 8 people. In Canada with a 
population of approximately 12,300,000 there were 1477 theaters in 
1946, having a total seating capacity of 758,640, a seat for every 17 
persons. The total number of admissions was 215,000,000 or 293 
per seat for the year. The average revenue per seat for the year was 
$72.00. 

Had each theater played to a full house at each performance atten- 
dance could have numbered 605,000,000. Actually, therefore, only 
37.6 per cent of the total seating capacity of the theater was utilized. 
It may be assumed that this figure will decrease because of the follow- 
ing trends: 



1 



1949 THEATER SITES 399 

1. Technological 

The development of television, bringing visual entertainment within 
easy reach of the individual and large groups as well. 

2. Social 

The increasing interest in home entertainment, which radio and 
television provide free. 

3. Economic 

The decrease in effective family income, because of reduction of 
industrial employment opportunities for women and the change from 
inflation to deflation in our economy. 

4 . Physical 

The increasing demand for up-to-date facilities and conveniences 
inside and outside the theater auditorium, because of competition 
with other forms of commercial entertainment and the increasing 
number of cars. 

5. Urban Development 

The decentralization of industries and the development of new 
residential areas on the fringe of established urban centers, which will 
make necessary new theater facilities at the expense of those already 
established in the regional area. 

In view of these trends, the theater operator who intends to build 
a new theater faces the following problems : 

(a) how to utilize more than 37 to 40 per cent of the potential 
seating capacity. 

(b) and consequently, how to achieve a profitable yearly revenue 
per seat. 

The answers to these problems cannot be provided simply by a 
mathematical formula, but only by considering a number of factors 
involved. 

6. Determining Factors of Revenue per Seat 

There are four major factors which directly affect the revenue per 
seat of a theater: 

(a) The class of picture the theater offers. (This depends largely 
on the films available in the motion picture film market and the de- 
mand of the population from which the theater draws its attendance, 
as related to age groups, purchasing capacity, spending habits.) 



400 FALUDI October 

(b) The location of the theater from the point of view of accessi- 
bility and the population density of the surrounding residential areas 
within a mile radius. 

(c) The size and design of the theater, which ultimately governs the 
capital investment and the operating costs. 

(d) The facilities provided by the theater inside and outside the 
auditorium. 

7. Importance of Location 

The importance of the location of the theater cannot be over- 
emphasized. Literally, many millions of dollars are involved in the 
selection of proper locations for theaters. There is no doubt that 
good pictures can modify temporarily the handicap of an inappropri- 
ate site but they cannot completely overcome this disadvantage. 

In order to analyze the specific locations that are more desirable 
than others, we shall distinguish the following areas, in which theater 
sites may be considered : 

1. Large urban centers. 

2. Fringe areas. 

3. Suburban neighborhoods. 

4. Small towns in the regional areas of large cities 

LOCATIONS OF THEATERS IN LARGE URBAN CENTERS 

The basic structure of a city is composed of several functional 
areas central retail and business sections, wholesale areas, indus- 
trial areas, residential districts, and their neighborhood shopping 
centers. These areas are generally scattered segments of a series of 
concentric circles. At the center is the financial and office district, 
immediately surrounding this is the central shopping area. In one 
section of the latter there is always a scattering of theaters, generally 
next to the window display stores. The motion picture theater tries 
to attract the man, or especially the woman, on the street. To do 
this, it must be easily accessible to the window-shopping crowd. 

The motion picture business has demonstrated clearly how proxim- 
ity of competing houses aids business. In many cities, all the down- 
town motion picture houses are located on one street, and even 
within three or four adjoining blocks. 

A survey and analysis of retail centers of 24 cities in 20 different 
states, covering 135 blocks, reveals an interesting pattern and relation- 
ship between theaters and .stores. 



1949 THEATER SITES 401 

According to this survey, theaters represent 10.7 per cent of all 
store units, while restaurants represent 9.2 per cent. The next types 
in order of importance are shoes, jewelry, and men's furnishings, each 
about 5 to 6 per cent, women's clothing stores, candy, drug, cigar 
stores, each about 2 to 3 per cent. Restaurants and snack bars are in 
nearly every block where there is a theater. Moreover there are almost 
as many restaurants in a block containing theaters as there are theaters. 

With the exception of downtown areas, theaters show no strong 
tendency to be grouped in the same blocks. In 135 blocks containing 
theaters, two theaters per block were found in only 13 cases, and three 
theaters per block in three cases. 

Generally speaking, in blocks containing theaters, the following 
store uses comprise one half of the total occupancies: theaters, 
restaurants, men's furnishings, shoes, jewelry, women's clothing, 
candy, drugs, and cigars. 

An important share of the retail business of the city is, however, 
conducted outside the central area in retail subcenters extending along 
major streets and in neighborhood shopping nuclei. In such loca- 
tions, the proximity of residential districts justifies the location of a 
theater. 

POPULATION AND THEATERS TORONTO 

An interesting study covering the city of Toronto indicates the 
lationship of population to theaters situated outside the downtown 
isiness center. The survey was conducted within concentric zones 
le mile apart. (See Figs. 2 and 3.) The first zone is around the 
mtral shopping area and the last one, 6 miles distant, takes in the 
fringe of the metropolitan area. Table II shows the number of people 
id theaters at various distances from downtown Toronto and the 
)pulation per theater seat. 

This tabulation reveals that the number of theaters and their 
iting capacity increase as the population increases up to the zone 
rhich is 3 to 4 miles from the downtown area. (See Figs. 4, 5, and 
6.) These figures then decrease to the limit of the urban area which 
is 6 miles from the center. Population per theater and per seat, how- 
ever, increases from about 4745 to 11,650 and from 5.16 to 17.93, 
respectively. The figures also indicate that the supporting popula- 
tion required per seat increases with the distance of the zones from the 
center, increasing by approximately 2 to 3 persons per mile. 
Another interesting feature of the survey is that there is a relation 



402 



FALUDI 



October 




1949 



THEATER SITES 



403 



between the number of the supporting population required and the 
density of residential population per acre, the purchasing capacity, 
and the spending habits of the residents. In high-density areas with 
low-income groups, the supporting population per seat varies from 
3.3 to 7. In low-density areas with high-income-class groups, it 
varies from 7 to 19. 

The nucleus of retail business along thoroughfares attracts the 
establishment of theaters. In Toronto, along three major thorough- 
fares, on a stretch of 6 miles, there are 25, 17, and 16 theaters, re- 
spectively. Along secondary thoroughfares for the same distance, the 
maximum number is 8, and the minimum is 1. Both these major and 

POPULATION 
250,000 



200, 000 



150,000 



100, 000 



50,000 



ZONES DOWN- TO I l~2 2"3 3"4 4"5 5'6 6+ MILES 
TOWN 

Fig. 3 Population on concentric one-mile zone. 

secondary thoroughfares possess a large number of scattered shopping 
and convenience goods stores, and carry a heavy concentration of 
vehicular traffic. 

LOCATIONS OF THEATERS IN FRINGE AREAS 

The Toronto survey shows that between the 5- and 6-mile zone 
there is a population of 73,000 with 8 theaters, having a total seating 
capacity of 6000. The average seating capacity of these theaters is 
750. The average number of people per theater is 9000 and per seat 
12. The location of the theater is closely related to the local shopping 
area, which consists of a large number of grocery, fruit, and vegetable, 
drug stores, meat markets, and other convenience goods outlets, 
interspersed with a lesser number of men's and ladies' wear stores. 
Almost without exception these stores draw customers from within 




404 



FALUDI 



October 



TABLE II 

RELATION BETWEEN THEATER LOCATION AND POPULATION PER SEAT 
(Data 1945 population map Town Planning Consultants Limited) 



Population 


Theaters 


Seats 


Persons 
per 
Theater 


Persons 
per 
Seat 


1. 


Downtown area 


7,000 


9 


13,583 


660 


0.52 


2. 


Within 1-mile 














radius exclud- 














ing the down- 














town area 


52,200 


11 


10,115 


4,745 


5.16 


3. 


Between 1- and 














2-mile radius 


138,900 


19 


16,566 


7,310 


8.41 


4. 


Between 2- and 














3-mile radius 


192,300 


28 


21,420 


6,868 


8.97 


5. 


Between 3- and 














4-mile radius 


217,300 


26 


21,042 


8,358 


10 . 33 


6. 


Between 4- and 














5-mile radius 


155,400 


19 


15,851 


8,179 


9.80 


7. 


Between 5- and 














6-mile radius 


73,200 


8 


6,092 


9,275 


12.00 


8. 


Beyond 6-mile 














radius 


93,200 


8 


5,198 


11,650 


17.93 



Metropolitan Area Toronto 
Total Population (1946 estimates, Dominion Bureau of Statistics) 

Persons per 

Population Theaters Theater 

959,308 128 7573 

easy walking distance, that is, from the area within a 3 /4-mile radius. 
It is obvious that a new theater here depends exclusively on the 
number of people living in such an area. 

LOCATION OF THEATERS IN SUBURBAN NEIGHBORHOODS 
The suburban neighborhoods are the frontiers of future urban 
development, and therefore they are potential locations for new types 
of shopping centers and theater sites. 

Both the United States and Canada have embarked on a vast hous- 
ing program. In the coming decade, in all likelihood, millions of 
homes will be built. The recognized trend is toward the establish- 
ment of residential districts in which residents share the common 
services, social activities, and facilities provided in the vicinity of the 



1949 



THEATER SITES 



405 




ZONES DOWN- TO I 
TOWN. 



1-2 2-3 3-4 4-5 5'6 6+ MILES 

Fig. 4 Theaters in concentric one-mile zones. 



dwelling. Such neighborhoods obviously depend on the larger urban 
centers for their basic employment, transportation, and cultural 
facilities. Their shopping centers should contain only the types and 
number of stores which can be well supported by their own population. 

However, if the shopping center is near to highway approaches 
from other areas, it frequently will draw a sizable portion of business 
from outside its tributary and trading area. It may attract attend- 
ance from the urban center itself if large parking areas are provided, 
and thus reverse the magnetic attraction of some theaters situated in 
the central area. 

The greater the increase of population in outlying areas, which is 
expected to result from the construction of urban freeways or limited- 
access highways providing access to the central city area, the greater 
will be the growth of outlying neighborhood business centers. 



ZONES DOWN- TO I \~2 2'3 3'4 4"5 5 '6 6+ MILES 




Fig. 5 Total theater seats in concentric one-mile zones. 



406 



FALUDI 



October 



In the Toronto metropolitan area, two large-scale neighborhood 
business developments with theaters are under preparation at present. 
In each case, the theaters planned will be twin buildings starting with 
an auditorium of 750 seats, which will be duplicated later as warranted 
by population increase. Parking facilities will be provided for over 
500 cars, or one parking space for every l l / 2 seats. 

LOCATION OF THEATERS IN SMALL TOWNS 

The small town is rapidly coming to the fore all over the country. 
It has been demonstrated that industry is tending to operate in a larger 
number of places rather than concentrating in already congested 




I -2 2-3 



3-4 



4-5 



5-6 



6 t MILES 



ZONES DOWN- TO I 
TOWN. 

Fig. 6 Persons per theater seat in concentric one-mile zones. 

areas. The small cities where industries are or may be located fall 
into two categories: those with a population between 10,000 and 
25,000 (there are 662 such towns in the United States); and those 
with a population between 25,000 and 50,000 (there are 212 such 
cities in the United States). 

Some of these are independent communities, depending on a 
metropolis in no major way. Another type is the suburban residen- 
tial city closely related, physically and economically, to a large city. 
There are also those small communities which are dependent upon a 
single industry, and are closely affected by its fluctuations. 

In all these communities new theaters with up-to-date facilities 
will be required as industrial and population growth will warrant it. 

When locating a theater in these communities a careful study will 
be required of existing theater facilities and population per seat, 
population growth, age groups, purchasing power, and spending 
habits as well as the characteristics of the business centers. 



1949 THEATER SITES 407 

CONCLUSIONS 

In the early stages of the motion picture industry the location 
of the theater was chosen by pure common sense and intuition. The 
theater industry had no tradition, and had to find its own way by 
experimental and empirical methods. However, with the help of 
land economics, sociology, and physical planning, we are able to deter- 
mine with scientific exactness, the characteristics of the dynamic or- 
ganism of the city. We are also able to identify the reasons for con- 
stant flux of the retail structure in the urban areas in response to eco- 
nomic forces. As the theater is part of the urban retail structure, to a 
large degree, it succeeds or fails as its location within the city struc- 
ture is favorable or unfavorable. 

Today the selection of the location is more important than ever 
because of the new trends already mentioned. 

The following are the basic steps in determining the suitability 
of a location or site : 

1. To determine the size of the population from which the antici- 
pated attendance will be drawn, within a radius of 1 to 2 miles. 

2. To identify the social and economic groups of the area tributary 
to the theater and the living and spending habits within these groups ; 
also to identify the age composition of the population and to deter- 
mine the population density and population growth. 

3. To study the retail pattern of the area, the accessibility of the 
site, traffic conditions, and transportation facilities. 

4. To define future residential, industrial, or commercial develop- 
ments and probable changes in the area with reference to planning 
projects (new housing, zoning, slum clearance, and highways). 

5. To consider these findings in relation to existing theaters in the 
area, their seating capacity, and population per seat in the tributary 
area. 

6. To evaluate all findings in relation to capital investment in 
land and building, anticipated operating costs, and revenue. 

While we should remember that special conditions prevail in each 
community, this suggested technique will assist with certainty, in 
selecting a desirable location for a theater. 

BIBLIOGRAPHY 

(1) Richard U. Ratcliff, "The Problem of Retail Site Selection," Michigan 
Business Studies, vol. 9, no. 1, University of Michigan, Ann Arbor, Michigan, 
1939. 

(2) "Motion Picture Theatres, Exhibitors and Distributors in Canada," 
Dominion Bureau of Statistics, Canada, 1946. 



New Portable High- Intensity 
Arc Spotlight* 

BY RUSSELL J. AYLING 

STRONG ELECTRIC CORPORATION, TOLEDO 2, OHIO 

Summary The spotlight to be described includes many features which are 
the result of an extensive investigation of desirable characteristics in such 
devices. An integral transformer supplies low-voltage alternating current 
to the arc from any 115-volt, alternating-current outlet at a drain of only 10 
amperes. A double-element variable-focus optical system allows the spot 
size to be continuously adjusted with negligible light loss. 

INTRODUCTION 

FOR MANY YEARS there has been a need in theatrical and allied 
fields for a lightweight portable spotlight of extremely high in- 
tensity. The operator either depended upon an incandescent or verti- 
cal arc-type spotlight for short projection distances, or the large the- 
ater-type spotlights which employ heavy rotating equipment and 
tremendous power consumption. The Strong "Trouper" designed for 
use in theaters, auditoriums, and night clubs is an answer to this need. 



Featuring an automatic carbon feed, the new "Trouper" produces a 
brilliant white, uniformly illuminated, and clear-cut spot, which sup- 
plies that extra sparkle to a performance, obtainable only with the 
use of high-intensity carbon arcs. With a color temperature of ap- 
proximately 5700 degrees Kelvin, as measured with an Eastman color 
temperature meter, the brilliancy of spot greatly surpasses any incan- 
descent or vertical low-intensity carbon-arc spotlight and actually will 
equal many of the large high-intensity types. 

The "Trouper," with a net weight of 215 pounds, has been devel- 
oped with the thought in mind of simplicity, portability, and ease of 
operation. It takes a new operator only a few moments to master ef- 
ficiently the operation of this well-balanced spotlight. 

The power requirements are extremely modest. Drawing 10 am- 
peres from a 115-volt outlet, the power rating is only 1 kilowatt. The 
following description of the design and operation of the "Trouper" 
covers (1) base and power supply, (2) lamp and optical system 

* Presented June 10, 1949, at the Central Section Regional Meeting, Toledo, Ohio. 
408 OCTOBER, 1949 JOURNAL OF THE SMPE VOLUME 53 



ARC SPOTLIGHT 



409 



mounting channel, (3) lamphouse, (4) lens optical system, (5) color 
boomerang, (6) optical system calculations, and (7) "Trouper" and 
television. 

BASE AND POWER SUPPLY 

The rigidly constructed base serves a dual purpose in supporting 
the lamp and optical system, and also housing the power supply. 
(Fig. 2.) The base is mounted on three rubber casters making it readily 





Fig. 1 "Trouper" spotlight. 



portable. If it is desired to have a more rigid mounting for permanent 
installations, three jackscrews are provided and adjusted until the 
weight has been shifted from the casters to the screws. 

The power supply is a compact, highly efficient, adjustable, trans- 
former which reduces a 115-volt, 60-cycle, alternating-current supply 
to 21 volts at the arc. If desired, special transformers can be supplied 
for practically any voltage or frequency range. The transformer is 
mounted underneath the base, in an out-of-the-way location. 



410 



AYLING 



October 



The standard 115-volt transformer is designed with a manual tap- 
changing system to allow for any commercial voltage variations be- 
tween 95 to 135 volts. The conveniently located coarse tap adjust- 
ment has three leads mounted on a terminal block. The line-feed wire 
is connected to the terminal having the voltage marking most nearly 
equal to the local voltage condition. If a finer adjustment is desired, 
an eight-position dial switch efficiently serves the purpose. A quick 
twist of the switch in the desired direction will instantly change the 
power consumption without extinguishing the arc. 



STEADYING HANDLE 




AC LINE CORD 



POWER SUPPLY 
_NAME PLATE 



LINE VOLTAGE S 
FREQUENCY PLATE 



Fig. 2 Base and power supply. 

An indicating voltmeter eliminates guesswork in ad justing the trans- 
former for proper arc voltage. The meter dial is equipped with a 
green zone. When the needle is in the center of the green zone, the 
correct power is being supplied to the arc, and the correct gap will be 
maintained. 

The top section of the base, called the yoke-and-cradle assembly, is 
connected to an adjustable, tubular column. This allows the optical 
centerline of the spotlight to vary in height from 46 to 58 inches. 
Practically any working condition can be mastered within this range. 

A five-wire braided electrical cord, connected to the transformer is 
neatly concealed by running through the tubular column to the yoke 
terminal box. The three control wires are connected to a polarized 



1949 ARC SPOTLIGHT 411 

twistlock receptacle, and the two heavier power wires are connected 
to individual electrical jacks. 

A horizontal swing-lock lever, and a vertical tilt-lock lever mounted 
on the yoke, can be set to give the required amount of friction to suit 
the individual operator, when following a moving act. The spotlight 
can be swung through a full 360 degrees horizontal travel, tilted down to 
angles of 45 degrees or more, and tilted up to approximately 30 degrees. 

LAMP AND OPTICAL SYSTEM MOUNTING CHANNEL 
A heavy-gauge-steel U-shaped channel is employed to give a preci- 
sion mounting platform for the lamp and optical system units. Being 
4*/2 feet in length this channel is rigidly reinforced to guard against 
any bending or twisting moments that might occur. 

The lamp and optical system are mounted separately in this channel 
and each is held securely in optical alignment by three conveniently 
located screws. The channel is fastened to the base cradle by four 
easily inserted retaining screws. This makes the "Trouper" easily dis- 
assembled into two units for shipment. 

LAMPHOUSE 

The rigid lamphouse is designed to accommodate an alternating- 
current high-intensity carbon arc. (Fig. 3.) The correct carbon trim 
is two 6-mm X 7-inch National alternating-current high-intensity, 
copper-coated carbons which operate at 45 amperes and 21 volts. 

The carbons, having a burning rate of 4.3 inches per hour, are fed 
automatically from a lead screw, which is rotated by a 20-revolution- 
per-hour synchronous drive motor. At this rate, a full trim of car- 
bons will burn for 1 Va hours. Tiiis precision method of feeding results 
in a constant arc gap, and essentially no carbon drift. The carbons 
are held securely in the jaws by a special heat-resistant leaf spring. 
By use of a lifting cam the spring is decompressed rapidly for changing 
carbons. Knobs, for manual striking of the arc, and focus adjustment 
of the arc, extend through the rear of the lamp in a convenient location. 

A silvered, glass reflector, elliptical in shape, efficiently collects the 
arc-crater light and directs it to a circular aperture. The crater is 
magnified 7 3 /s times its original size at this aperture. The physical 
dimensions of the reflector are 3 x /4-inch focal length, 24-inch working 
distance, and 10V4-inch diameter. 

Horizontal and vertical reflector tilt adjustment handles, project 
through the rear of the lamp, and assure quick alignment of the pro- 
jected carbon crater on the aperture hole. To keep the reflector free 



412 



AYLING 



October 



from copper deposits caused by carbon sputtering or falling molten 
copper, a special heat-treated glass deflection shield, 2 x /2 inches by 4 
inches, is inserted between the arc and bottom portion of the reflector. 
The copper deposits will collect on this shield which can be replaced 
from time to time at very little cost. There is negligible light loss as a 
result of this glass. A special safety feature is a door-operated line 
switch to assure that all power to the arc is turned off when the 
lamphouse door is open. Another line switch (toggle-type) is con- 
veniently located at the top rear section of the lamp. 

The lamphouse, constructed entirely of sheet metal, has a large 
cubical content for the size of the arc, resulting in a cool operating 




LEAD SCREW 
LEAD SCREW 



Fig. 3 Lamphouse. 



lamp. The lamphouse door is equipped with a colored glass window 
for viewing the arc characteristics. An arcescope screen, located at 
the top rear of the lamp, projects a side pinhole image of the carbons 
for convenience to the operator in keeping a correct focus. 

A five-wire braided cord, from the lamp, is plugged into the yoke 
terminal box, thereby completing the circuit to the power supply. 
This method of electrically connecting the lamp and base provides 
for quick disconnect when disassembling the "Trouper" into two 
units. Many times the operator must trim the lamp in semidarkness. 
A door-operated trimming light adds to his convenience. 

LENS OPTICAL SYSTEM 

The lens optical system is a new method of efficiently utilizing all 
light passing through the aperture. (Fig. 4.) 



1949 



ARC SPOTLIGHT 



413 



A two-element, variable-focal-length lens system, which continu- 
ously focuses on the aperture, is used to project the desired spot sizes. 
This system consists of a 2 1 /2-inch focal length, 2-inch diameter double 
convex pyrex lens, and an 18-inch focal length, 7-inch diameter plano- 
convex objective lens. A handle mounted on the side of the large 
lens carriage controls the variation of projected spot size. This han- 
dle may also be utilized to vary the angularity of the spotlight to main- 
tain the spot on a moving act. 

A specially designed linkage is provided to control the relative 
movement between the two lenses. The linkage properly adjusts, au- 
tomatically, the distance between the lenses as they are moved to- 
ward or from the light source. A clear-cut spot is created at any po- 




LENS 

POSITIONING 
RIBBON 



Fig. 4 Lens optical system. 



sition. A spot-sharpness focusing control slightly changes the rela- 
tive position of the lenses, to compensate for variation of projection 
distances. 

The aperture plate, upon which the lens optical system is focused, 
has three positions of use, and is actuated by a conveniently located 
handle. In position 1, a 1 V4-inch-diameter hole emits the light, and 
will allow a variation in spot size from a small spot to a stage flood. 
From minimum to maximum positions, the spot diameter will in- 
crease seven times. Position 2 is a 3 / 4 -inch-diameter hole, used only 
for a small head spot. Position 3 can be used as a dowser. A quick 
flip of the aperture handle and any one of these positions can be ob- 
tained instantaneously. As an example of spot-size variation for a 
60-foot throw, the P/Vinch-diameter aperture will handle spot sizes 
from 4y 2 feet to 32 feet in diameter. With the 3 / 4 -inch aperture a 2 l / r 
foot head spot can be obtained. 



414 AYLING October 

A masking shutter is provided for stripping a spot horizontally when 
desired. The shutter blades are adjustable to compensate for off- 
normal projection that might occur. In the closed position the shut- 
ter can also serve as a dowser. Both the aperture and masking shut- 
ter are constructed of Vs-mch brass with a nickel plating to withstand 
the intense heat to which they are subjected. 

The optical-system housing can be removed with very little effort, 
simply by loosening the three knurled screws holding the housing to 
the lamphouse, and the single knurled screw, securing the forward end. 
A lens-access hole is located conveniently to allow cleaning of the lenses 
without disassembling. 

COLOR BOOMERANG 

The boomerang is equipped with six color filter slides and a special 
track for inserting an ultraviolet (black-light-type) filter. 

The operation of the individual color filter is accomplished by manu- 
ally lifting the desired handle to the uppermost position. A perma- 
nent magnet located in the top of the boomerang holds the filter se- 
curely in position. The color is released by gently pushing the handle 
downward until it disengages from the magnet, and letting it fall in 
place. The color slides are easily removable for inserting new colors. 

OPTICAL-SYSTEM CALCULATIONS 
The basis for the optical system calculations is the lens formula 1 

- = - + - (l) 

/ w V 

f = focal length of lens 

where u = object distance 

V = image distance. 

Substituting in (1) for the small lens we find that as HI is smaller 
than /i, for this case, FI is a virtual image, so the sign becomes nega- 
tive. Therefore, 

l-l _JL 

/i Mi" 1 " -Fi 






To calculate the large lens position, we know that u 2 is tn"e object 
distance (Fig. 5). So from (1) 

L ._ I . J_ 

f* u z T V , 



or m = ~^j. (3) 



1949 



ARC SPOTLIGHT 



415 



Now we wish to find the distance d between the two lenses, so by ob- 
servation (Fig. 5) 






Substituting (2) and (3) we obtain 

!// 

d = 



- / 2 



d + ui = 



Mi 5 



2 -f t 



(4) 
(5) 



Therefore for any distance u\ of the small lens, and a known pro- 
jection distance F 2 , we can readily calculate the position of the large 
lens to obtain a sharp, clear-cut spot. 

s 




v 2 



Fig. 5 Lens optical system. 



F 2 
t/2 



focal length of small lens. A 

object distance for small lens. D 

image distance for small lens. S 

focal length of large lens. / 

object distance for large lens. R 



aperture diameter, 
distance between lenses, 
diameter of projected spot, 
virtual image, 
reflector. 



image distance for large lens. 



It is evident that the small lens creates a virtual image of the aper- 
ture. The large lens focuses on this virtual image and projects it to 
the desired location. 

Table I shows the various distances of the large lens from the aper- 
ture as the small lens distance is varied. For these calculations the 
projected throw (F 2 ) is 60 feet. 

TABLE I 



u\, Inches 


d + Ui, Inches 


ui, Inches 


d + ui, Inches 





18.47 


1.50 


16.22 


0.25 


18.44 


1.75 


14.39 


0.50 


18.34 


2.00 


10.47 


0.75 


18.15 


2.125 


6.43 


1.00 


17.80 


2.160 


4.75 


1.25 


17.22 


2.1875 


3.12 



416 AYLING 

The projected spot size can also be calculated by the product of the 
magnification formula for each lens. 1 

! - ^ (6) 

A M 2 Mi 

S = projected spot diameter 
A = aperture diameter. 

Substituting (2) and (3) we arrive at 



A i * - m 

= A h <F=W 

"TROUPER" AND TELEVISION 

The more recent type of television camera tubes are the image orthi- 
con 2 RCA-5769 and RCA-5655. They are recommended for outdoor 
pickup use, but are also suitable for studio use, where the illumination 
is greater than about 50 foot-candles. 

The spectral response of these tubes has a high blue, good green, 
useful red, and practically no infrared sensitivity. Absence of infra- 
red response permits portrayal of colors in more nearly their true 
gradation. 

The "Trouper," with extremely high intensities and a color temper- 
ature in the blue region, is well suited as a light source for television 
pickup. In most studios it can be located 30 to 35 feet from the tele- 
vised object, resulting in intensities up to about 2000 foot-candles, and 
an over-all illumination of 6000 lumens. 

The "Trouper" is practically noiseless in operation, and under ac- 
tual test operations, it has been found that no noise interference is 
picked up by the microphone. 

REFERENCES 

(1) J. Valasek, "Elements of Optics," McGraw-Hill Book Company, New York, 
New York, p. 67. 

(2) RCA Tube Handbook News, "Image Orthicon Type 5769," Commercial 
Engineering, RCA, Harrison, New Jersey, issue 49B. 



PROGRESS MEDAL AWARD 



AT THE BANQUET held on October 12, 1949, during the 66th 
Semiannual Convention of the Society, Dr. Harvey Fletcher 
was presented with the 1948 Progress Medal Award, given for out- 
standing achievement in motion picture technology. 

Dr. Fletcher was born September 11, 1884, at Provo, Utah. He 
received a B.S. degree from the Brigham Young University in 1907, 
and a Ph.D. degree from the University of Chicago in 1911, and 
numerous honorary degrees from other institutions of higher learn- 
ing in the United States. 

Dr. Fletcher was Professor of 
Physics at Brigham Young Univer- 
sity from 1911 to 1916, when he 
left the university to join the Re- 
search Department of the Bell Tele- 
phone Laboratories. In 1933 he 
was appointed Director of Physical 
Research at the Bell Telephone 
Laboratories, a position which he 
still holds. 

For a period of over thirty years, 
he has contributed immeasurably 
toward an understanding of the 
fundamental nature of speech and 
hearing. The results of his work 
appear in the design of microphones , 
equipment for electrical recording 
of speed and other sounds, and the 
development of loudspeakers which 
reproduce sound with high fidelity. His studies on hearing and the 
effect of sound intensity on aural frequency response were a sub- 
stantial contribution to the motion picture art which led to record- 
ing techniques now used in the production of motion pictures. His 
development of facilities for transmitting music played by the 
Philadelphia Orchestra in the city of Philadelphia to Washington, 
D. C., by wire were a substantial early contribution to the somewhat 
later development of stereophonic recording. His work has done 
much to advance the art of transmission and recording of speech. 
The Progress Medal was awarded to Dr. Fletcher 

"in recognition of his outstanding contributions to the art of motion pic- 
ture sound recording and reproduction." 




HARVEY FLETCHER 



SMPE SAMUEL L. WARNER 
MEMORIAL AWARD FOR 1949 

EACH YEAR THE SOCIETY has the privilege of presenting the 
Samuel L. Warner Memorial Award to an engineer selected by! 
the Society for outstanding technical work in the field of sound! 
motion pictures. This award was established by the Warner] 
brothers in memory of their brother Samuel L. Warner, who was a 
pioneer in the production of sound motion pictures. 

This year the award was presented 
to Ralph M. Evans on October 12, 
1949, for 

"his outstanding work in color motion 
picture films and related subjects." 

Mr. Evans, a Fellow of the So- 
ciety, is superintendent in charge of 
the Color Control Department at 
the Eastman Kodak Company, 
where he has served in this capacity 
since the formation of the depart- 
ment in 1946. The function of the 
department is to maintain quality 
control orl all color photographic 
processes at the Eastman Kodak 
Company and to carry on develop- 
ment work on these processes after their release to the public. 
Prior to the organization of the Color Control Department, Mr. 
Evans was in the Research Laboratories of the Eastman Kodak 
Company in charge of the development of color photographic 
processes. As part of this work he conducted a considerable 
amount of research on visual effects in photography, and this 
work is continuing under his direction. 

Mr. Evans first came to Eastman Kodak in 1928. Later he was 
away from the Company for six years, employed by the Twentieth 
Century-Fox Film Corporation and DeLuxe Laboratories. This; 
time was spent on color photography and control and development 
work in black-and-white motion picture photography. 




RALPH M. EVANS 



He is past chairman of the Color Committee of the Society, and 
as the representative of this organization, he is on the Inter-Society 
Color Council. During the past two years he has served as chair- 
man of the Inter-Society Color Council and is now a member of its 
Executive Committee. He is also a member of the Color Committee 
of the Illuminating Engineering Society. 

Mr. Evans is well known for his illustrated lectures on color and 
color photography, which have been delivered in all parts of the 
country to scientific and technical societies. 

Mr. Evans has written a comprehensive book* called "An Intro- 
duction to Color" which divides the subject of color into three sec- 
tions physics, psychophysics, and psychology. This is a new 
approach to the subject, and Mr. Evans' years of experience provide 
a background for this broad viewpoint. 

He is a graduate of Massachusetts Institute of Technology where 
he majored in optics and photography and received the degree of 
Bachelor of Science in physics. 

* Reviewed in the JOURNAL for February, 1949, page 236. 

; JOURNAL AWARDS 1949 

THE JOURNAL AWARD for 1949 was presented to Mr. Fred G. 
Albin on October 12, 1949, for his paper "Sensitometric Aspect 
of Television Monitor-Tube Photography," published in the Decem- 
ber, 1948, issue of the JOURNAL. 

Fred G. Albin was born in Springfield, Ohio, on December 11, 

; 1903. He received his education as electrical engineer from the 
University of California at Berkeley and California School of Tech- 

j nology at Pasadena. 

In 1930 he became associated with United Artists and Goldwyn 
Studios in Hollywood as research engineer of sound recording, em- 

i bracing the fields of acoustics, audio frequency, and photography. 

, He gained renown for advancements in variable-density sound re- 
cording, contributing several articles to the JOURNAL of the SMPE. 
In 1940 he became associated with the Radio Corporation of 
America as development engineer. During the war he developed 
high-powered radio-frequency generators for industrial applications. 
Toward the end of the war he developed large-screen television 
projectors of the instantaneous type; also the kinescope recording 
systems now extensively used by television broadcasters. 







In his paper, which is an outstanding and well-detailed report of 
an engineering study, Mr. Albin reviews the practices of cathode- 
ray tube photography on motion picture film. He analyzes, from 
the standpoint of conventional photographic sensitometry, the 
photographic and electronic aspects of television film recording 
procedures that are currently in use. 

Picture reproducibility is a diffi- 
cult problem, because the combined 
gammas of the several elements of a 
typical television system do not ap- 
proach unity and therefore an origi- 
nal scene picked up by a television 
camera cannot be faithfully repro- 
duced by a subsequent linear photo- 
graphic process without resorting 
to some practical form of gamma 
correction. 

The author shows that this prob- 
lem can be solved through the use 
of nonlinear electrical circuits which 
are designed to produce an over-all 
television system gamma of approxi- 
mately 1.5. Modern photographic 
techniques can then produce a re- 
sulting motion picture film record 
equals conventional prac- j 




FRED G. ALBIN 

that " 

tice in motion picture professional 
photography/' 



Honorable Mention was awarded 
to Mr. Charles R. Fordyce for his 
paper, "Improved Safety Motion 
Picture Film Support/' which ap- 
peared in the October, 1948, issue of 
the JOURNAL. 

Mr. Fordyce presents with utmost 
clarity and in a very readable style 
the history of the recent develop- 
ment of a safety film support which 
is suitable for professional motion 
picture use as a base for either 35- 
mm negative or release positive film. 
His report follows this new film base 
through its several stages of labora- 




C. R. FORDYCE 



tory development into commercial "trade tests" that were designed 
to provide comparative performance data between the new safety 
film and conventional nitrate release positive film. 



Mr. John A. Maurer received 
Honorable Mention for his paper, 
"Optical Sound-Track Printing/' 
published in the May, 1948, issue of 
the JOURNAL. 

Mr. Maurer reviews current com- 
mercial practices in the printing 
of motion picture sound track, ex- 
plaining the nature of the more 
serious defects produced in the 
printed film, together with a study 
of contributing causes. By way 
of solution, he presents in remark- 
ably understandable language, the 
detailed history of the development 
of a printer differing markedly from 
conventional types. 




JOHN A. MAURER 



Fellow Awards 1949 

AT THE BANQUET held on October 12, 1949, President Sponable 
presented the Fellow Award to the fourteen members of the 
Society whose names are listed below: 



JOSEPH E. AIKEN 

Naval Photographic Center 

GERALD M. BEST 
Warner Brothers Pictures 

DANIEL J. BLOOMBERG 
Republic Studios 

i HERMAN H. DUERR 
Ansco Corporation 

ALLEN B. DuMoNT 

Allen B. DuMont Laboratories, Inc. 

FERDINAND L. EICH 
Paramount Pictures, Inc. 

PHILO T. FARNSWORTH 
Farnsworth Television and Radio Cor- 
poration 



CHARLES R. FORDYCE 
Eastman Kodak Company 

LORIN D. GRIGNON 
Twentieth Century-Fox Films 

M. A. HANKINS 
Mole-Richardson Company 

GARLAND C. MISENER 
Ansco Corporation 

EDWARD S. SEELEY 
Altec Service Corporation 

JOHN E. VOLKMANN 
RCA Victor Division 

FRED WALLER 

Vitarama and Cinerama Corporations 



Book Reviews 



Electron Tubes 

Volume 11935-1941; Volume 111942-1948 

Published (1949) by RCA Review, Princeton, N. J. Volume I 475 pages + x 
pages. 238 illustrations. Q l / t X 9 inches. Price, $2.50; $2.70 outside of the 
United States. Volume II 454 pages + x pages. 241 illustrations. 6 : / 4 X 9 
inches. Price, $2.50; $2.70 outside of the United States. 

These two volumes contain 40 reprints of papers and 52 summaries of papers 
on the subject of vacuum-tube theory and practice. They were all written by 
RCA authors and have been collected in these volumes from the many scientific 
and technical journals in which they originally appeared between the years 1935 
and 1948. The papers and summaries in each volume have been divided into 
four groups: general, transmitting, receiving, and special. Each volume also 
contains a bibliography of additional papers and articles by RCA authors on 
vacuum tubes and related topics which have appeared in journals and trade 
papers. The bibliography in Volume I has some 400 items published between 
1919 and 1941 while that in Volume II has 170 published between 1942 and 1948. 

Although the papers in these volumes have all been available for some time to 
those with access to a fairly complete library of scientific periodicals, motion 
picture engineers in general who are interested in the theory and application of 
electron tubes will be grateful to the Radio Corporation of America for bringing 
together from many widely scattered sources these contributions from RCA 
workers. Motion picture sound engineers will find many of these papers of pa - 
ticular interest and value if they are not already familiar with them. 

L. F. BROWN 

Consulting Engineer 

1236 Green Acre Ave. 

Hollywood 46, Calif. 



The Sound Track Book of the Theatre 

Published (1949) by The Sound Track, 1001 W. Washington Blvd., Chicago 7, 
Illinois. Also available from Motiograph, Inc., 4431 W. Lake St., Chicago 24, 
Illinois, and from Motiograph dealers. 440 pages -f- 5-page index. 315 illustra- 
tions and diagrams, 6X9 inches. Price: $10.00. 

The finest symposium of the theater to be published in years. This book covers 
the entire field of the theater and consists of reprints of the most important articles 
appearing in the magazine, The Sound Track. 

Part One PROJECTION- AND SOUND covers minutely every part of the pro- 
jector from intermittents and shutters to belts and bearings. Naturally the 
chapters lean heavily on Motiograph design and equipment but it is written with 
a wide enough scope so that the information is applicable to any type of projec- 
tion equipment. 
422 



Book Reviews 



Part Two THEATRE MANAGEMENT is of special interest to theater executives. 
j As in Part One, all forms of management problems including programming, 
I exploitation, accounting, acoustics, air conditioning, and theater design are 
thoroughly discussed by authorities in their particular field. 



Part Three RECENT THEATRE DEVELOPMENTS brings information on three 
new projects that have recently come before the industry, namely, Drive-ins, 
Television, and Stereophonic Sound. 

Detailed plans, including approximate qosts, are given for building and equip- 
ping a modern Drive-in Theater. 

The article on Theater Television, while basic in form, covers the essentials of 
transmission and reception. Several misconceptions are cleared up and a prac- 
tical system of theater television equipment is presented. 

Excellent quality reproductions of photographs, diagrams, and cartoons on 
nearly every page brighten the book considerably. 

This book should be of the greatest interest to every theater owner, executive, 
and projectionist and as a manual should be in every theater in the country. 

WILLIAM K. AUGHENBAUGH 

Crosley Broadcasting Corporation 

Cincinnati, Ohio 



SMPE Officers and Committees 

The names of Society Officers and of 
Committee Chairmen and Members are 
published annually in the April issue of the 
JOURNAL. Changes and corrections to these 
listings are published in the September 
JOURNAL. 



423 



Current Literature 



THE EDITORS present for convenient reference a list of articles dealing with 
subjects cognate to motion picture engineering published in a number of 
selected journals. Photostatic or microfilm copies of articles in magazines that | 
are available may be obtained from The Library of Congress, Washington, D. C., I 
or from the New York Public Library, Now York, N. Y., at prevailing rates. 
American Cinematographer British Kinematography 

vol. 30, no. 7, July, 1949 vol. 154, no. 1, July, 1949 

India's Movie Industry (p. 236) The Kinema and Town Planning 



C. DEVlNNA 

Du Pont's New Color Film (p. 240) 

V. B. SEASE 
Translucent Photo Backgrounds Cut 

Production Costs (p. 240) P. 

TANNURA 
The Research Council Camera Crane 

(p. 242) F. E. LYON 
The Animars (p. 248) J. D. HAYES 

and K. PESTRECOV 

vol. 30, no. 8, August, 1949 
The New Nord Camera (p. 282) 

D. HOFFMAN 

Some Do's and Don't's for TV Film 
Photography (p. 283) C. LORING 

Color Compensating Filters Simpli- 
fied (p. 284) A. ROWAN 

Kinevox is Newest of Magnetic Film 
Recorders (p. 292) 

New Hallen Recorder Announced 

(p. 299) 
International Projectionist 

vol. 24, no. 7, July, 1949 

Distortion Factors in Sound Repro- 
duction. Pt. II (p. 5) R. A. 
MITCHELL 

Cadmium-Mercury Vapor Lamps: 
Present Status (p. 8) H. B. SELL- 
WOOD 

British vs. American Projectors (p. 
10) R. H. CRICKS 

vol. 24, no. 8, August, 1949 

Lens and Film Factors Affecting 
Focus (p. 5) R. A. MITCHELL 

The Great Enigma: The Stereo- 
scopic Perspective (p. 13) T. 
NAKKEN 
424 



(p. 1) C. WILLIAMS 
Make-up and the Motion Picture. 
I. Make-up in Relation to the 
Photographic Emulsion (p. 9) 
E. TAYLOR 
Communications 

vol. 29, no. 7, July, 1949 
TV 16-mm Pulsed-Light Projector 
(p. 14) H. B. FANCHER 

vol. 29, no. 8, August, 1U 
The Limitations of Sound Recording 

(p. 28) S. J. BEGUN 
International Photographer 

vol. 21, no. 7, July, 1949 
New Triple Head Color Printer (p. 
20) P. A. Roos and C. R. HALLO- 
WELL, JR. 

Du Pont Synthetic Positive Color 
Film Being Demonstrated (p. 24) 

vol. 21, no. 8, August, 1949 
MGM's 25th Anniversary (p. 5) 
New High-Speed Camera (p. 18) 
Radio Engineering News 

vol. 52, no. 1, July, 1949 
Sound Mixer for TV Film Recording 

(p. 12) 
RCA Review 

vol. 10, no. 2, June, 1949 
Method and Multiple Operation of 
Transmitter Tubes particularly 
Adapted for Television Trans- 
mission in the Ultra-High-Fre- 
quency Band (p. 161) G. H. 
BROWN, W. C. MORRISON, W. L. 
BEHREND, and J. C. REDDKCK 
Development and Performance of 
Television Camera Tubes (p. 173) 
R. B. JANES, R. E. JOHNSON, and 
R. S. MOORE 



To the Editor 



In the article by J. E. Bates and I. V. Runyan, which appeared in the July, 
1949, issue of the JOURNAL, the regeneration of Ansco Color bleach solutions by 
the use of liquid bromine is disclosed (pp. 16-17). We believe it is only fair to 
your readers to inform them of the legal situation regarding the use of liquid 
bromine in bleach regeneration. The method is the subject of a patent applica- 
tion assignable to Pavelle Color Incorporated. (Tne term liquid bromine is 
stressed to distinguish from bromine water which had been tried by others and 
discarded because of bath dilution.) Before anyone spends time and money 
installing this process, he should know that its use may not be entirely free. 

We have delayed publishing our data and experience on bleach regeneration 
pending patent-office action on our application, but will prepare a paper in the 
near future. 

The article by A. H. Brunner, Jr., P. B. Means, Jr., and R. H. Zappert in the 
same issue contains a statement which we believe to be incorrect. They state on 
page 30 that the colorimetric method of Varden and Seary (/. Soc. Mot. Pict. Eng., 
vol. 47, pp. 450-453; December, 1946) for ferrocyanide determination is not 
sufficiently accurate for bromine regeneration. For over three years we have 
controlled the regeneration of thousands of gallons of bleach by the colorimetric 
method. Even with the crude apparatus described in our article, it is easy to 
determine the ferrocyanide concentration within an accuracy of plus or minus 
0.03 per cent. We have found this to be entirely adequate. 

EUGENE G. SEARY 

Chief Chemist 

Pavelle Color, Incorporated 

New York 19, N. Y. 

European Advisory Committee 

A Continental Division of the SMPE European Advisory Committee has been 
appointed by the President of the SMPE. The Division Chairman is L. Didiee, 
President of the AFITEC (Association Franchise des Igenieurs et Techniciens 
du Cinema), and members are 

R. BOCQUEL Television Engineer 

G. MARESCHAL Technical Manager of Societe G.T.C. 

and M. TERRUS (asst.) Technical Manager, Eclair 

J. CORDONNIER Technical Adviser for Acoustics 

and R. ALLA (asst.) Technical Manager Cin6ac (exhibitors) 

M. YVONNET Manager Sound Recording Dept., Eclair 

and M. CERTES (asst.) Manager Sound Recording Dept., Pathe- 

Cine"ma Studios 
S. FELDMAN Technical Manager, Paris Studios Cinema 

and J. FOURRAGE (asst.) Lighting Equipment, Eclair Studios 

J. Vivi6 Permanent Secretary of the AFITEC 

The purposes of the Continental Division and the British Division of our 
European Advisory Committee are to serve as liaison between the General Society 
and organizations interested in motion picture engineering. They also will report 
on foreign developments of interest to Society members and will aid the Papers 
Committee whenever likely JOURNAL material appears. 

425 



New Products 



Further information concerning the material described below can 
be obtained by writing direct to the manufacturers. As in the case 
of technical papers, publication of these news items does not consti- 
tute endorsement of the manufacturer's statements nor of his products. 



New Filament Lamp 

A 3000-watt incandescent lamp to 
compete with arc lamps for spotlighting 
stage shows has been developed by 
General Electric's Lamp Department 
at Nela Park, Ohio. 

Producing an estimated 900,000 
candle power in properly designed 
equipment, the new spotlight is in- 
tended primarily for lighting the stage 
from distances of 75 to 150 feet. It is 
seen by General Electric's illuminating 
engineers as suitable for outdoor 
theaters, sports arenas, auditoriums, 
itinerant spectacles, and other applica- 
tions where the long-distance projec- 
tion of an intense beam of light is re- 
quired. 

Because of its simplicity of operation 
in a well-constructed fixture, and be- 
cause of its advantages over arc spot- 
lights, the lamp is seen by lighting de- 
signers as permitting the application of 
professional stage-lighting techniques 
to retail store fashion shows and other 
demonstrations. It is expected to be 
used widely in television lighting. 

The new lamp is tubular in shape, 
four inches in diameter and nearly a 
foot long. Of bipost construction, it is 
intended to be burned vertically in a 
base-up position. This causes blacken- 
ing to occur outside of the pickup range 
of the reflector, thus contributing 
greatly to the prolonged efficiency of 
the lamp. It has a rated burning life of 
100 hours. 

The lamp's light output is not sub- 
ject to variations common to arc 
lamps. Unlike arc lamps, the lamp 

426 



can be dimmed as desired. The cur- 
rent required is half that of a 70- 
ampere, direct-current arc, thereby 
permitting more light for the same 
wiring capacity. At a throw of 100 




feet, it gives an average of 90 foot- 
candles of light for a spot six feet in 
diameter, an amount equal to the il- 
lumination from a 70-ampere arc. At 
wider spreads, it can produce greater 
illumination than even higher current 
arcs. 



New Products 



Further information concerning the material described below can 
be obtained by writing direct to the manufacturers. As in the case 
of technical papers, publication of these news items does not consti- 
tute endorsement of the manufacturer's statements nor of his products. 



The lamp is used in a special fixture 
which forms an accurately controlled 
beam and provides flexibility in beam 
pattern. The first equipment to be 
built for the lamp is the Dyna-Beam 
Klieglight, manufactured by Kliegl 
Brothers of New York City. Since 
the 3000-watt lamp employs standard 
voltages, and may be used on either 
!ilt( 'mating- or direct-current circuits, 
arc-lamp generating equipment is elimi- 
nat ed, and with no carbon adjustments 
to make, one man can handle several 
units. 

Balanced "TV" Tripod Head 

The Camera Equipment Company, 
1600 Broadway, New York 19, New 
York, has announced a new balanced 
"TV" tripod head. This pan and tilt 
head meets the strict requirements of 
televison technicians and is a distinctly 
new concept of pan and tilt action, 
whereby friction and gyro principles 
have been discarded. 

Floating action is experienced with 
the balanced "TV" tripod head. Even 
in pans or tilts of slight degree, or pans 
of 360 degrees, extra smooth action is 
realized. The tilt is balanced to assist 
the television cameraman in the opera- 
tion of his camera, which reduces to a 
minimum the amount of effort re- 
quired to move the camera. 

The balanced "TV" head relieves 
the operator from additional strain 



and eliminates the possibility of acci- 
dents. If, because of neglect on the 
part of the operator, the head is left 
unlocked with the camera mounted, 
it cannot fall forward or backward. 
The pan handle is adjustable for the 
operators' comfort, with no play be- 
tween the pan-handle mounting 




bracket and the head. To adjust the 
position a simple locking lever is re- 
leased, adjustment made, and lever 
repositioned. The pan handle is an 
adjustable telescoping type. 

The weight and manufacture of the 
camera to be used must be known to 
achieve proper tension and accomplish 
floating action. A special "TV" size 
tripod base with reinforced shoes can 
be supplied for the head which can also 
be mounted on all standard profes- 
sional-type tripod bases, perambula- 
tors, pedestals, and dollies. 



427 



Statement of the Ownership, Management, Circulation, Etc., Required by the 
Act of Congress of August 24, 1912, as Amended by the Acts of March 3, 1933, 
and July 2, 1946, of Journal of the Society of Motion Picture Engineers, published 
monthly at Easton, Pa., for October 1, 1949. 

State of New York ) 
County of New York ) ss 

Before me, a Notary Public in and for the State and county aforesaid, person- 
ally appeared Boyce Nemec, who, having been duly sworn according to law, de- 
poses and says that he is the Executive Secretary of the Journal of the Society of 
Motion Picture Engineers and that the following is, to the best of his knowledge 
and belief, a true statement of the ownership, management (and if a daily, 
weekly, semiweekly, or triweekly newspaper, the circulation), etc., of the aforesaid 
publication for the date shown in the above caption, required by the Act of August 
24, 1912, as amended by the Acts of March 3, 1933, and July 2, 1946, embodied 
in section 537, Postal Laws and Regulations, printed on the reverse of this form, 
to wit: 

1. That the names and addresses of the publisher, editor, managing editor, 
and business managers are: 

Name of Post Office Address 

Publisher, Society of Motion Picture Engineers, Inc., 342 Madison Ave., New 

York 17, N. Y. 

Editor, Helen M. Stote, 342 Madison Ave., New York 17, N. Y. 
Managing Editor, None. 
Business Manager, Boyce Nemec, 342 Madison Ave., New York 17, N. Y. 

2. That the owner is: (If owned by a corporation, its name and address 
must be stated and also immediately thereunder the names and addresses of 
stockholders owning or holding one per cent or more of total amount of stock. 
If not owned by a corporation, the names and addresses of the individual owners 
must be given. If owned by a firm, company, or other unincorporated concern, 
its name and address, as well as those of each individual member, must be given.) 
Society of Motion Picture Engineers, Inc., 342 Madison Ave., New York 17, N. Y. 
Earl I. Sponable, President, 460 W. 54 St., New York 19, N. Y. 

Robert M. Corbin, Secretary, 343 State St., Rochester 4, N T . Y. 
Ralph B. Austrian, Treasurer, 25 W. 54 St., New York 19, N. Y. 
No stockholders. 

3. That the known bondholders, mortgagees, and other security holders 
owning or holding one per cent or more of total amount of bonds, mortgages, or 
other securities are: (If there are none, so state.) 

None. 

4. That the two paragraphs next above, giving the names of the owners, 
stockholders, and security holders, if any, contain not only the list of stockholders 
and security holders as they appear upon the books of the company but also, 
in cases where the stockholder or security holder appears upon the books of the 
company as trustee or in any other fiduciary relation, the name of the person or 
corporation for whom such trustee is acting, is given; also that the said two 
paragraphs contain statements embracing affiant's full knowledge and belief 
as to the circumstances and conditions under which stockholders and security 
holders who do not appear upon the books of the company as trustees, hold stock 
and securities in a capacity other than that of a bona fide owner; and this affiant 
has no reason to believe that any other person, association, or corporation has 
any interest direct or indirect in the said stock, bonds, or other securities than 
as so stated by him. 

5. That the average number of copies of each issue of this publication sold 
or distributed, through the mails or otherwise, to paid subscribers during the 
twelve months preceding the date shown above is : (This information is required 
from daily, weekly, semiweekly, and triweekly newspapers only.) 

BOYCE NEMEC, Exec. Secy., Business Manager. 
Sworn to and subscribed before me this 19th day of September, 1949. 

(Seal) Elisabeth J. Rubino 
Notary Public, Clerk's No. 41-3390800, 
Queens County. 
(My commission expires March 30, 1951) 






Journal of the 

Society of Motion Picture Engineers 



r OLUME 53 



NOVEMBER 1949 



NUMBER 5 



PAGE 

Motion Pictures in the Guided-Missile Program H. M. COBB 431 

High-Speed Motion Picture Photography 440 

High-Speed Motion Pictures by Multiple-Aperture Focal-Plane Scanners. . 

FORDYCE E. TUTTLE 451 

Improvements in High-Speed Motion Pictures by Multiple- Aperture Focal- 
Plane Scanners FORDYCE E. TUTTLE 462 

Twenty-Lens High-Speed Camera CHARLES W. WYCKOFF 469 

Half-Million Stationary Images per Second with Refocused Revolving 

Beams C. D. MILLER 479 

Very-High-Speed Drum-Type Camera. . .K. M. BAIRD AND D. S. L. DURIE 489 

Design of Rotating Prisms for High-Speed Cameras. . . . JOHN H. WADDELL 496 
Recent British Equipment and Technique for High-Speed Cinematography 

G. A. JONES AND E. D. EYLES 502 

Bowen Ribbon-Frame Camera E. E. GREEN AND T. J. OBST 515 

Physical Optic Analysis of Image Quality in Schlieren Photography 

H. JEROME SHAFER 524 

Exposure Meter for High-Speed Photography E. T. HIGGONS 545 

Techniques in High-Speed Cathode-Ray Oscillography 

C. BERKLEY AND H. P. MANSBERG 549 

Measuring Shock with High-Speed Motion Pictures J. T. MULLER 579 

High-Speed Motion Pictures in Full Color FRANKLIN M. TYLEE 588 

Water-Cooled High-Pressure Mercury-Discharge Lamp for Direct-Current 

Operation W. ELENBAAS AND E. W. VAN HEUVEN 594 

New View Finder for the Fastax Camera ALFRED L. LIDFELDT 598 

Report of High-Speed Photography Committee 602 

A. G. D. West '. 604 

Book Reviews: 

"The Blue Book of Audio- Visual Equipment," Published by Business 
Screen Magazine and The National Association of Visual Education 
Dealers 

Reviewed by Paul R. Wendt 605 

"Look and See," by Colin Beale 

Reviewed by Paul R. Wendt 605 

Meetings of Other Societies 606 

New Products 607 

Employment Service 608 



iRTHUR C. DOWNES 

Chairman 
Board of Editors 



HELEN M. STOTE 
Editor 



NORWOOD L. SIMMONS 

Chairman 
Papers Committee 



Jription to nonmembers, $12.50 per annum; to members, $6.25 per annum, included in 
annual membership dues; single copies, $1.50. Order from the Society's General Office, 
discount of ten per cent is allowed to accredited agencies on orders for subscriptions and 
single copies. Published monthly at Easton, Pa., by the Society of Motion Picture Engineers, 
Inc. Publication Office, 20th & Northampton Sts., Easton, Pa. General and Editorial Office, 
342 Madison Ave., New York 17, N. Y. Entered as second-class matter January 15, 1930, 
at the Post Office at Easton, Pa., under the Act of March 3, 1879. 

Copyright, 1949, by the Society of Motion Picture Engineers, Inc. Permission to republish 
material from the JOURNAL must be obtained in writing from the General Office of the Society. 
Copyright under International Copyright Convention and Pan-American Convention. The 
Society is not responsible for statements of authors or contributors. 



Society of 

Motion Picture Engineers 

342 MADISON AVENUE NEW YORK 17, N. Y. TEL. Mu 2-2185 
BOYCE NEMEC . . . EXECUTIVE SECRETARY 

OFFICERS 

1949-1950 



PRESIDENT 
Earl I. Sponable 
460 W. 54 St. 
New York 19, N. Y. 

EXECUTIVE 
VICE-PRESIDENT 
Peter Mole 

941 N. Sycamore Ave. 
Hollywood 38, Calif. 



PAST-PRESIDENT 
Loren L. Ryder 
5451 Marathon St. 
Hollywood 38, Calif. 

EDITORIAL 
VICE-PRESIDENT 
Clyde R. Keith 
120 Broadway 
New York 5, N. Y. 



1948-1949 



ENGINEERING 
VICE-PRESIDENT 
John A. Maurer 
37-0131 St. 
Long Island City 1, N. Y. 



TREASURER 
Ralph B. Austrian 
25 W. 54 St. 
New York 19, N. Y. 



SECRETARY 
Robert M. Corbin 
343 State St. 
Rochester 4, N. Y. 

CONVENTION 
VICE-PRESIDENT 
William C. Kunzmann 
Box 6087 
Cleveland 1, Ohio 

1949 

FINANCIAL 
VICE-PRESIDENT 
David B. Joy 
30 E. 42 St. 
New York 17, N. Y. 



1948-1949 

Alan W. Cook 
4 Druid PI. 
Binghamton, N. Y. 



Lloyd T. Goldsmith 
Warner Brothers 
Burbank, Calif. 



Paul J. Larsen 
508 S. Tulane St. 
Albuquerque, N. M. 



Gordon E. Sawyer 
857 N. Martel Ave. 
Hollywood 46, Calif. 



Governors 
1949 

James Frank, Jr. 
1310 Peachtree Battle 

Ave., N. W. 
Atlanta, Ga. 

William B. Lodge 
485 Madison Ave. 
New York 22, N. Y. 

William H. Rivers 
342 Madison Ave. 
New York 17, N. Y. 

'Sidney P. Solow 
959 Seward St. 
HoUywood 38, Calif. 

R. T. Van Niman 
4431 W. Lake St. 
Chicago 24, 111. 



1949-1950 

Herbert Barnett 
Manville Lane 
Pleasantville, N. Y. 



Fred T. Bowditch 
Box 6087 
Cleveland 1, Ohio 



Kenneth F. Morgan 
6601 Romaine St. 
Los Angeles 38, Calif. 



Norwood L. Simmons 
6706 Santa Monica Blvd 
Hollywood 38, Calif. 



otiori Pictures in the 
uided- Missile Program* 

H. M. COBB 

SRDEEN PROVING GROUND, ABERDEEN, MARYLAND 



Summary Methods of obtaining ballistic data on long-range and guided 
missiles in the Army Ordnance Department's missile program at White 
Sands Proving Ground are described. The use of motion pictures for ob- 
taining trajectory measurements and information on detailed flight perform- 
ance of missiles launched at the White Sands range has produced a signifi- 
cant wealth of data for use of ballisticians and design engineers engaged in 
the development of long-range guided missiles. 



I HE USE OF MOTION PICTURES as a method of obtaining ballistic 
data on full-scale, free-flight missiles and guided missiles has 
employed at the White Sands Proving Ground, New Mexico, 
since the summer of 1945. At that station, where the Army Ordnance 
Department, in collaboration with other departments of the Armed 
Services, conducts flight tests of high-altitude and long-range missiles, 
the Ballistic Research Laboratories have installed and operate sev- 
eral types of motion picture instruments by means of which a variety 
of experimental work is carried out in connection with the missile 
program. 

Theoretical and experimental work on the development of observing 
methods and instrumentation is performed by the Ballistic Research 
Laboratories at Aberdeen Proving Ground. These methods and 
instruments are applied at the White Sands range for the purpose of 
obtaining basic data to be used by design engineers in the development 
of new weapons. 

Other methods of obtaining ballistic data are used also since observ- 
ing conditions, the different types of data required, accuracy require- 
ments, time limits to be met, and the cost of the entire missile project 
make it impractical to depend upon a single method. Both ground- 
and missile-borne instruments of electronic as well as optical types 

* Presented October 13, 1949, at the SMPE Convention in Hollywood. 

NOVEMBER, 1949 JOURNAL OF THE SMPE VOLUME 53 431 



432 



COBB 



November 



are employed. Thus data obtained by one system may be checked 
against that obtained by a completely independent system, or the 
data from one system may be augmented by data from another sys- 
tem. Since we are here concerned primarily with motion picture 




Fig. 1 Bowen-Knapp camera with timing device. Exposures are of 
Vio.ooo-second duration, may be taken at rates between 30 and 180 per second, 
the corresponding field sizes being 5 1 /t inches by 0.9 and 0.15 inch, respectively. 
The instrument may be equipped with either a 7- or 12-inch focal-length lens. 



records a brief description of the instruments used and the variety o: 
data obtained will illustrate the usefulness of the method in this field 
Near the launching position fixed motion picture cameras, especially 
designed for wide field, are used to observe take-off or launching per- 
formance of the missiles. By means of triangulation from a set 
two or more of these stations located approximately one mile from the 



1949 



GUIDED-MISSILE PROGRAM 



433 



launching stand the position of the missile at a given time may be 
determined to an accuracy of about six inches up to an altitude of 
approximately 3000 feet. These cameras normally are operated at 
30 frames per second with an exposure time of one ten-thousandth of 
a second. A high accuracy of the measurements and the details of 
missile performance observed during the critical launching phase have 
constituted a very significant wealth of data to the design engineers. 
Trajectory data beyond the field of the fixed cameras are obtained 




Fig. 2 Bowen-Knapp camera record of a V-2 shortly after launching 



by use of tracking phototheodolites which record on each frame the 
azimuth and elevation of the optical axis at the time of exposure as 
well as the picture of the missile. From the position of the missile 
image within the frame the tracking error is measured, hence the 
direction of the missile from the station may be obtained to an accur- 
acy of approximately 20 seconds of arc. The shutters of all instru- 
ments are actuated synchronously from a central station. The in- 
struments were originally built with optical systems of 12 and 24 
inches focal length but recent modifications have included cassegrain 
systems up to 180 inches focal length. 



434 



COBB 



November 




Fig. 3 Askania cinetheodolite, modified with casse- 
grain optical system of 15 feet focal length. Exposures 
may be made to a maximum rate of 4 per second, with 
simultaneous recording of azimuth and elevation of optical 
axis. 



GUIDED-MISSILE PROGRAM 



435 



k 9 
Jthough the phototheodolite observations do not meet the highest 
accuracy requirements they are capable of furnishing a trajectory in a 
comparatively short time. Under normal atmospheric conditions 
observations are obtained on a V-2 missile to an altitude of approxi- 
mately 35 miles, beyond which other types of observations may be 
available or a vacuum trajectory may be computed. 




Fig. 4 Twin 4.5-inch tracking telescope on modified M-45 mount, showing 
recording and tracking instruments. The effective focal length may be varied 
from 15 to 35 feet, and 35-mm photographs taken at rates up to 20 exposures 
per second. 



During the early stages of the high-altitude missile program it was 
recognized that long-focus instruments would be required for obtain- 
ing detailed information regarding flight performance at missile dis- 
tances beyond the range of those described above. To meet this need 
the development of long-focus tracking instrumentation was started 
at the Ballistic Research Laboratories. The first instrument, built 
as an experimental model, consisted of a 4.5-inch refracting telescope 
of 60 inches focal length mounted in conjunction with an auxiliary 



436 



COBB 



November 



lens near the prime focus to produce an effective focal length of 
approximately 240 inches. This optical system was mounted, with 
a standard motion picture camera, on an M-45 machine-gun turret 
which was in turn mounted on a standard 37-mm gun carriage. 

The instrument was first tested at the White Sands Proving Ground 
in May, 1946, and indicated a promise of such valuable observations 
of missiles at great distances that development and construction of 




Fig. 5 10-inch tracking telescope on modified M-45 mount. The effective 
focal length may be varied between limits of about 18 and 40 feet. 



larger instruments of the same general type were initiated. The next 
two instruments developed were mounted in essentially the same way 
as the first but consisted of 10-inch Newtonian reflectors with effective 
focal-length variable between approximately 20 and 40 feet. The 
successful application of these instruments led to the construction of a 
16-inch Newtonian reflector on an M-2 90-mm gun mount, capable of 
operating with effective focal lengths between 40 and 80 feet. 



1949 



GuiDED-MissiLE PROGRAM 



437 



Observations obtained by these instruments have given informa- 
tion, not only as to how the missiles performed but in a number of 
instances why they performed as they did. Functional failures, 
separation of booster rockets, and ejection of experimental apparatus 




Fig. 6 16-irich tracking telescope on modified 90-mm 
mount, of effective focal length from 40 to 80 feet. The in- 
strument is located 40 miles from the launching site, at an 
elevation of 800Q feet. 



from the missiles may be observed. Photometric and spectrographic 
studies of the jet flame at high altitudes and at high velocities have 
furnished information regarding fuel-burning processes and heat dis- 
tribution within the jet and have given an indication of aerodynamic 
flow patterns around the base of the missile. Orientation of the 



438 COBB November 

missile axis and rate of spin may be determined from these motion pic- 
ture observations with a high degree of accuracy. Orientation of the 
axis of a V-2 at an altitude of 20 miles has been determined with a prob- 
able error of 0.6 degree. 




Fig. 7 4.5-inch tracking telescope 
photograph of A-4 missile, at a distance 
of 8 miles, taken with a 20-foot focal 
length. Not reproduced portion of 35- 
mm frame contains azimuth, elevation, 
and time records. 



These instruments already have shown their usefulness in the ballis- 
tic-measurements field and have pointed the direction in which future 
development should move. Studies of tracking systems, drive sys- 
tems, control systems, recording methods, and problems of 



1949 GUIDED-MISSILE PROGRAM 439 

atmospheric transmission of light are being continued at the Ballistic 
Research Laboratories. Further development of long-focus motion 




Fig. 8 Sample frames at 10-second intervals of tracking telescope record of 
A-4 missile during period of propulsion, showing changing jet structure. 
Corresponding slant ranges vary from 8 to 20 miles. 

picture instruments necessarily will depend upon progress in the 
guided-missile program. New problems of observation will furnish 
the guide line in research on methods of measurement. 



High-Speed Motion Picture 
Photography* 



ARE TWO METHODS of taking high-speed motion pictures 
_ widely used in the United States today. Furthermore there is 
work being conducted at present which will combine both of these 
methods into a third method. 

The first general group are those motion pictures made by the use 
of a continuously moving film camera and an associated trigger cir- 
cuit which fires a high-voltage gas-discharge tube at a selected fre- 
quency. This particular method has been developed by Dr. Harold 
Ei* Edgerton and his associates at the Massachusetts Institute of 
Technology. 

The first work done in this field was to use a gas-discharge lamp to 
secure single exposures with a view camera. The gas-discharge tube 
consists of either a glass or a quartz tube which is filled with a rare 
inert gas such as xenon and possibly krypton added to it. There is 
an electrode on both ends of the tube and a third electrode outside 
of the tube. A high-voltage direct-current potential of approximately 
2000 volts, though the voltage may be considerably higher, is kept 
across the first two-mentioned electrodes. The gap is great enough 
so that breakdown does not occur. This high direct-current potential 
is stored in a capacitor having a capacity of from 0.3 microfarad to 
1300 microfarads. When an induced high voltage (from 10,000 to 
15,000 volts) is applied to the third electrode on the grounded side 
of the capacitor ionization of the gas takes place which lowers its 
resistance and permits the stored charge in the capacitor to discharge. 
This discharge through the inert gas causes a very brilliant flash of 
short duration. The capacitor and the external resistance of the 
circuit are the controlling factors of the actual time of the flash. In 
the first work done along this line a raw spark in air was fired in the 
same manner and using a smaller capacitor but of the same or higher 
voltage. Flashes occurring in from */% to 2 microseconds were easily 
obtained. The gas tubes as now generally used work from 1 to 
2000 microseconds. 



* Presented April 6, 1949, at the SMPE Convention in New York. 
440 NOVEMBER, 1949 JOURNAL OF THE SMPE VOLUME 53 






HIGH-SPEED PHOTOGRAPHY 441 

The General Electric Company has developed a circuit which is 
similar to the Edgerton circuit but instead of using the gas tube as 
described above a high-pressure mercury- vapor lamp namely the H6 
is used. With this particular lamp and its associated circuit, flashes 
of 1 to 2 microseconds' duration are obtained at a very high energy 
level. 

With a continuously moving film camera and a commutator for 
firing the lamps in synchronism with the film movement the fre- 
quencies can be stepped up considerably so that up to 3000 pictures 
per second can be obtained from a given firing circuit. However, 
recently, electronic switching equipment has been developed so that 
six circuits may fire into a given tube to obtain pictures up to 20,000 
per second. In the computation of the picture-taking speed and the 
film speed it is necessary to balance the exposure time or the duration 
of the flash so that it causes no blur on the film as the film is moving 
continuously. Therefore, the shorter the flash the better the result 
in terms of a produced photographic image. If the film is moving 
at 100 feet a second and a flash occurs in 1 microsecond the film will 
move 1.2 mils which is within the resolving power of the films used in 
high-speed motion picture photography. In taking pictures of this 
type, no shutter is used, hence under ordinary circumstances the room 
must be darkened sufficiently to prevent the film from being fogged 
by extraneous room light. This type of photography has been used 
very extensively in many types of industrial research in providing 
solutions to problems which have been troublesome to engineers for 
many years. There has been developed recently a unit which fires 
the lamp up to rates of 10,000 per second and furnishes sufficient 
illumination to light a field 12 inches square. The power supply 
needed for this is 2 1 /z kilowatts and the exposure time is 1 microsecond 
per flash. The larger units supplied with the General Radio Com- 
pany circuit will provide sufficient illumination to light a compara- 
tively large field. Higher picture-taking rates than these stated 
above can be used when. the subject is in silhouette or photographed 
by the schlieren method. Methods of schlieren photography will be 
discussed later. 

Another application of the gas-discharge-tube technique is to use 
the flashing lamp as a multiple-exposure device on a stationary piece 
of film. If the rate of firing is known, it is possible to compute 
acceleration and deceleration of various subjects under study by 
opening the shutter, starting the flashing lamp, having the test 



442 HIGH-SPEED PHOTOGRAPHY November 

subject go through its operation once, and closing the shutter. In this 
way a multiple image is obtained, and knowing the subject distance 
and focal length of the lens, it is possible to compute rates of 
movement. 

With the increasing use of the single-flash technique it has been 
necessary to develop shutters which would fire the gas-discharge lamp 
at the instant the shutter was fully opened. Older techniques re- 
quired that a slow shutter or the open-flash method be used, but 
shutters have been developed recently by the major lens manu- 
facturers which are synchronized with the flash and at shutter speeds 
as high as l / m second. It has been learned, however, that using 
short focal length lenses may step this figure up to 1 / 7B o or Yiooo 
second. 

The rotating-prism motion picture cameras are the most commonly 
used high-speed cameras today because of their portability. These 
cameras are light in weight, can run from either alternating or direct 
current and have lenses available of varying focal length. In the 
case of the Kodak high-speed camera, lenses of 2 J /2- and 4-inch focal 
length are available with other focal lenses available on special order. 
With the Western Electric Fastax camera, there are lenses available 
in focal lengths from 35 mm to 15 inches and development is pro- 
ceeding on a 30-inch lens. 

The Kodak high-speed camera used 16-mm film and operates 
through the range of 1000 to 3000 pictures per second. Variable 
speeds lower than 1000 frames a second can be obtained through the 
use of a continuously adjustable autotransformer such as a Variac. 
The optical image moves in synchronism with the film through the 
use of a rotating plane-parallel glass plate of precise thickness which 
is located between the lens and the film. Two frames are exposed 
for each rotation of this plate, and a speed of 90,000 revolutions per 
minute is attained at 3000 pictures a second. The exposure per 
frame is equal to the reciprocal of 5 times the camera speed. For 
example, at 1000 frames per second the exposure time per frame is 
1 / 16,000 of a second. 

A 32-volt universal-type motor operates the camera. To limit 
acceleration strain, a mechanically coupled rheostat gradually reduces 
resistance until the preset terminal voltage is attained. At 3000 
frames a second, the terminal input to the motor is equal to the full 
line voltage, usually about 115 volts. 



1949 HIGH-SPEED PHOTOGRAPHY 443 

An automatic switch within the camera is preset to cut off the cur- 
rent supply at the end of a run. This switch may be set for either 
a 50- or 100-foot length of film. A synchronizing switch can be set 
either to open or close an external circuit at any time during a run. 
This supplementary circuit permits the subject being photographed 
to start ahead of, simultaneously with, or after the camera has begun 
to operate. When the camera is operated on 60-cycle current, a 
built-in argon lamp flashing 120 times a second exposes this number 
of traces along the edge of the film. Accurate determination of the 
speed at any instant during a run can be made by counting the 
number of frames between two consecutive traces and multiplying by 
120. 

The Kodak high-speed camera uses a telescopic type of view finder 
wherein by looking through the eyepiece it is possible to compose and 
focus the image directly on a piece of matte-surface film which is in- 
serted in the aperture. 

In the case of the Fastax cameras, of which there are three, an 
8-mm 10,000-picture-per-second camera, a 16-mm 5000-picture-per- 
second camera, and a 35-mm wide-angle 3500-picture-per-second 
camera, the film-loading situation is comparatively simple. The 
Fastax is loaded by placing the feed spool on the feed spindle, pulling 
about a 12-inch length of film off, and pulling the knob on the hold- 
down roller out, and then moving that assembly upward on its axis 
counterclockwise. The film is then placed on the sprocket with the 
perforations in engagement with the teeth. Care must be taken 
to be sure that the film is inserted between the timing lamp and the 
sprocket teeth properly and not in interference with the timing lamp. 
The free end is then placed into the take-up spool, the take-up spool 
placed on the take-up spindle, and the slack taken out of the film. 
The door is then closed and the camera is ready to be operated. The 
Fastax camera does not require a starting resistor for the two motors 
on the camera which are rated at 120 volts. One motor drives the 
sprocket and prism assembly while the other motor drives the take-up 
spindle. When starting, the take-up motor has a tendency to run a 
little faster than the driving motor and consequently the film is kept 
under tension and assistance is given the driving sprocket with this 
tension that exists. The acceleration is such that the motors cannot 
be started above 150 volts without ripping the film. 

A 4-sided prism is used for the 16- and 35-mm Fastax cameras and 
an 8-sided prism for the 8-mm Fastax camera. In the case of the 



444 HIGH-SPEED PHOTOGRAPHY November 

8-mm cameras, those now in manufacture have a prism which is the 
same length as that of the 16-mm camera so that by substituting the 
aperture plate with one whose slits are twice as long as provided, a 
full-width 16-mm picture is obtained, with an 8-mm frame height. 
This will prove of advantage in making ballistic studies and detona- 
tion-rate studies as well as burning of fuel in cylinders. It will be 
necessary for the customer to provide his own aperture plate for this 
change. 

In the case of the Fastax camera, where the film is mounted on a 
sprocket when operated, the lens is focused at the plane of the aerial 
image which is approximately 6*/2 mils above the surface of the 
sprocket. There are four holes in the sprocket. By rotating the 
sprocket by hand until one of the holes is lined up with the rotating 
prism, when the prism faces are perpendicular to the optical axis, the 
image formed by the objective lens is picked up on a ground glass on 
the door of the camera. This image is projected on to the ground 
glass by first having passed through a right-angle prism, through a 
32-mm microscope objective, through another prism, and on to the 
ground glass. There is a little trap door in the housing which should 
be at right angles to the door of the camera as pictures are being 
taken. If there is a bright light back of the camera and the trap is 
open, the sprocket holes are exposed on the film. 

It is possible by using a 3 / 8 -inch punch to view the subject up until 
it is ready to be taken by punching a hole in the middle of the 
frame of the film. This hole is lined up with the hole in the sprocket 
and focusing is done normally. This hole should be punched about 
from 12 to 18 inches from the end of the film so that the camera can 
be loaded normally and be ready for use. 

The Fastax camera is also equipped with a V4-watt argon-lamp 
timer. The l /rwatt argon lamps can be actuated directly from 120- 
volt, 60-cycle alternating current which will lay down 120 pips per 
second, or it can be operated from an oscillator which will drive the 
lamp with a square-top wave. In order to increase the intensity of 
the lamp to provide an image which is stronger, the voltage may be 
increased to 135 to 150 root-mean-square volts. In the event that the 
x /4-watt argon lamps (AR-3) are broken, the replacement lamp should 
be burned on 60-cycle, 120 -volt alternating current for 24 hours 
in order to age them, otherwise there may be a lack of stabilization 
between the firing voltages of the two electrodes. If a square-wave 
oscillator is used it is not necessary to do this since only one electrode 



1949 HIGH-SPEED PHOTOGRAPHY 445 

is activated. In measuring the length between the pips from the 
beginning of one to the beginning of the next with the 60-cycle pulse 
the time interval will be & l /a milliseconds. However, with an unaged 
lamp, it is necessary to measure from the beginning of one pulse to the 
beginning of the second pulse from the first one and consequently 
this measurement is 16 2 / 3 milliseconds. 

The Potter Instrument Company of Long Island City has built an 
oscillator which will furnish 1000 pips per second for operating up to 
14 high-speed-camera timing lamps simultaneously. This oscillator 
used a 100-kilocycle crystal control and the timing circuit is then 
derived from breaking the 100,000-cycle output of the crystal to 1000 
through two decade reductions. This oscillator can be operated from 
either 60-cycle or 400-cycle, 120-volt circuits. The 400-cycle circuit 
permits using this equipment in aircraft. 

It has been observed that the human eye and brain cannot assimi- 
late many actions going on simultaneously upon a screen. There- 
fore, in taking high-speed pictures the primary rule of photographic 
composition is to make the picture as simple as possible by confining 
the subject under study to one of its component actions rather than 
the subject as a whole. If, for example, a calculating machine is being 
photographed, individual springs, cams, locking levers, and similar 
devices should be photographed separately rather than attempting to 
make a high-speed picture of the whole unit at once. Greater magni- 
fication is obtained when the single subject is photographed. If 
possible, there should be some color contrast so as to delineate the 
actions as they occur from static or stationary parts. 

Then comes the problem of lighting this in the laboratory. For- 
merly, the lights used for high-speed photography were quite bulky; 
750-watt, 2000-watt, and 5000-watt lamps in reflectors have been 
employed. As a general thing a spherical reflector was placed back 
of the lamp so that the image of the filament would be projected 
on the subject. There were other cases, however, in which reflector- 
type lamps were used such as the RSP-2 750-watt photospot, airplane 
landing lamps (for portable use in planes), and 150- watt show-window 
spots when burned at 220 volts after preheating. The older type 
lamps as mentioned above have been extremely effective for lighting 
small subjects or when banks of them were used for lighting subjects 
up to roughly 24 by 24 inches. Most high-speed-camera subjects 
fall within this field. When using the lamps mentioned above, 
particularly the 750-watt and 2000-watt setups, lamps were secured 



446 HIGH-SPEED PHOTOGRAPHY November 

which were rated at 100 volts. When they were set up on the sub- 
ject, two lamps burned in series so that each lamp burned at approxi- 
mately 60 volts. In the case of the Fastax camera when the shadow 
density was observed through the ground glass with this setup and 
by stopping down the lens, an exposure would be correct for 5000 
pictures per second at between //5.6 and//8 depending upon the color 
and brightness of the subject. This guessing method has not been 
too satisfactory. When they were ready for picture-taking the 
lamps would be turned on to full brightness and used in parallel 
rather than series. There is available on the market today a very 
convenient series-parallel switch for this purpose, as well as for a new 
lamp which will be mentioned shortly. It is manufactured by the 
Industrial Timer Corporation, Newark, New Jersey. This par- 
ticular switch will accommodate four lamps and is known as their 
"HI-LO" switch. 

There has been recently developed by the General Electric Com- 
pany a "750R" high-speed photographic lamp. This particular lamp 
is designed to operate at about 18 inches from the subject and the 
candle power at that distance within 5 degrees of its axis is 75,000. 
Two of these lamps are adequate to make pictures of subjects up to 4 
by 4 inches at//5.6 at 5000 pictures per second. Using four of these 
lamps on the subject it is possible to take full-color Kodachrome pic- 
tures at 5000 pictures per second at //2. 

Mercury-arc lamps have not been satisfactory on alternating 
current because of their pulsing on and off. The Philips Company is 
using mercury arc for illuminating subjects powered with direct cur- 
rent so as to avoid flutter. Fluorescent lamps cannot be used be- 
cause of their fluttering and comparatively low intensity. One 
should consider that between approximately 100,000 to 500,000 foot- 
candles are necessary to take pictures under ordinary circumstances 
of high speed with the lens reasonably well stopped down. 

In order to eliminate many of the troubles that have been encoun- 
tered, the Weston Electrical Instrument Company is announcing an 
exposure meter for high-speed photography which will measure 
either incandescent light or sunlight. Edgerton earlier announced a 
high-speed gas-discharge-tube exposure meter. There will be pro- 
vided an index on the Weston meter for measuring values of light 
from 100 to 300,000 foot-candles. Three steps on the meter will be 
necessary in order to measure this range, and there will be attached to 



1949 HIGH-SPEED PHOTOGRAPHY 447 

the meter an exposure scale for both Super XX film and Kodachrome 
film, Type A. 

The high-speed cameras can be very satisfactorily used out of doors. 
Kodachromes have been obtained in New Mexico during the bright- 
light period of the day (10 A.M. to 2 P.M.) in the summertime at 1000 
pictures per second at //2. Furthermore black-and-white pictures 
have been successfully taken at speeds up to 4000 per second under 
reasonably brilliant lighting conditions out of doors. With special 
processing techniques, pictures have been taken under water in normal 
daylight at depths up to 10 feet at 4000 pictures per second (it is 
suggested that the subject be painted a light color for making such 
studies and that a reflective bottom, such as white sand, be present). 
Silhouette pictures can be taken at speeds up to 14,000 per second in 
daylight. 

In taking a picture of incandescent subjects it is often necessary to 
use neutral-density filters to cut down the light produced by the 
incandescent subject. A neutral density of 1.0 for example has a 
transmission of 10 per cent light, neutral-density filter of 2.0, 1 per 
cent, a neutral density of 3, Vio of 1 per cent, and so forth. In taking 
pictures of photoflash lamps burning it is necessary to use a neutral 
density of 3.0 to 4.0. Trial and error are about the best means of 
determining the exposures to be used for incandescent subjects. 

It has been found that the reciprocity loss on Kodachrome is con- 
siderably greater than on Super XX film and, therefore, the exposure 
factor between the two changes considerably. Instead of being 12 to 
1 as it is in normal daylight, the figure becomes from 32 to 64 times. 
There is a peculiar effect, however, that has not been explained and 
that is when a picture is taken on Kodachrome with a Fastax camera 
there is no noticeable difference between the beginning of the film 
and the end of the film on projection. In exposure it is noticeable if 
the two ends are placed one along side of the other. 

There are a number of films which can be used with high-speed 
cameras. For the 16-mm high-speed cameras, Kodak Super X, 
Super XX, and Kodachrome, Type A, reversal films are available as 
well as Kodak Super XX Negative, Linagraph Ortho, Linagraph Pan, 
and Super XX and Super X Blue Base Reversal Films. For the 
8-mm Fastax, only Kodak Super XX, Super X, and Kodachrome, 
Type A, reversal films are available. For the 35-mm Fastax camera, 
Linagraph Ortho, Linagraph Pan, and Kodak Super XX negative 
films are available. These are all Eastman Kodak Company 



448 HIGH-SPEED PHOTOGRAPHY November 

products and should be ordered from your local photographic dealer. 
It is essential that all orders for 16-mm film to be used in high-speed 
cameras specify, "Spooled for High-Speed Cameras." Film orders 
for the 8-Mm Fastax camera should specify, "Spooled for 8-Mm Fas- 
tax Camera." This assures the user that he will receive fresh film of 
highest emulsion speed and that it will be correctly perforated and 
spooled on aluminum spools without core clips. The use of other 
than aluminum spools will impair the dynamic balance of the camera, 
and should a core clip become detached at the end of a run, it would 
seriously damage the camera mechanism. 

The Linagraph Ortho and the Linagraph Pan are used in high- 
speed cameras when modified for use as an oscilloscope camera. 
Methods of high-speed oscillography will be discussed later. 

In making schlieren pictures several methods can be used. The 
first method is to use an incandescent lamp and image the filament of 
the lamp at the objective lens. The subject will pass between the 
lamp and the objective. In order to focus the lamp at the lens a 
spherical mirror can be placed back of the lamp. By adjusting the 
relationship between the mirror and the lamp it is easily possible to 
secure the image of the filament at the lens. The objective lens is 
then focused at the subject plane and not at the light source. 

A second method is to replace the spherical mirror with one or two 
condensing lenses in order to image the light source at the objective 
lens. 

A third method which has just recently been developed by Edger- 
ton and his associates has been to link the flashing lamp with the Ko- 
dak and Fastax high-speed cameras. The flashing lamp which they 
have developed for this purpose will be ideal for schlieren pictures, for 
the actual time of flash is 1 microsecond and it can be operated up to 
frequencies of 10 kilocycles. In this case the incandescent lamp is 
replaced by the new flashing lamp and there is a triggering device in 
the high-speed camera which allows the lamp to be fired when the 
picture frame is on line with the optical axis of the complete system. 
This type of light source is particularly adaptable for making schlieren 
pictures for the effective time of exposure is reduced considerably. 
The two first-mentioned systems would not resolve velocities of 
shock waves comparable with that of the method just mentioned. 

The third method can also be used to illuminate high-speed photo- 
graphic subjects from the front. This lamp will adequately light a 
field size 12 X 12 feet. There are several advantages in using this 



1949 HIGH-SPEED PHOTOGRAPHY 449 

method for the time of exposure is reduced to about 1 microsecond. 
Furthermore, the high-speed motion picture camera, either Kodak or 
Fastax, provides the necessary shutter action so that the unit can be 
used under fully lighted conditions. Prismatic aberrations caused by 
the angle of rotation in a rotating prism are eliminated, only those 
aberrations existing which are caused by the glass block itself re- 
maining. These new lighting units which can be synchronized quite 
easily with the Fastax or Kodak camera are available from Edgerton, 
Germeshausen, and Grier, Cambridge, Massachusetts. 

JBoth the Kodak and Fastax cameras can be used as ultrahigh- 
speed oscilloscopic recording cameras and frequencies up to one 
million cycles can be recorded as a continuous-wave trace and con- 
siderably above this if only the envelopes are required. In the case 
of the Fastax camera, the prism assembly is removed from the 
camera for this procedure. This can be done by removing the aper- 
ture plate and the four screws which hold the split plates. The prism 
shaft is then pulled out very carefully and the split plates removed as 
soon as they are clear. The prism shaft can then be completely re- 
moved. It is suggested that split-plate assembly be replaced by a 
single plate with four holes drilled in it so that film chips will not get 
down into the main drive assembly. It will be necessary to refocus 
the camera and use the visual focusing only on the ground glass and 
disregard the lens-focusing scale. In reassembling the camera the 
prism faces should be lined up so that the picture will be framed cor- 
rectly and not out either y 6 , 2 /5> 3 /5> or 4 / 5 of a frame because of mis- 
matching gear teeth. 

The Eastman Kodak Company does not recommend that owners of 
the Kodak high-speed camera attempt to modify their cameras for 
oscillographic work. It is recommended that such modification be 
made at the factory in Rochester. 

A Pll coating is used on the cathode-ray tube and additional inten- 
sifying voltages supplied. In the case of a 5-inch tube it is best to 
use voltages in the neighborhood of 6000 in order to get 350 kilo- 
cycles. A 2-inch-tube oscilloscope which is designed for this par- 
ticular unit when operating at 2000 volts will supply the necessary 
frequencies up to a million. Very fine relay chatter, blast fronts, 
velocities of projectiles, and many other subjects can easily be studied 
by this new method. 

There is a control unit now being made for the Fastax camera 
known as the J410 or "Goose." This unit is manufactured by the 



450 HIGH-SPEED PHOTOGRAPHY 

Industrial Timer Corporation, Newark, New Jersey, and has built 
into it a timing circuit which allows the Fastax Camera to be in- 
creased in speed over 40 per cent. The camera is started off at 130 
volts and 70 milliseconds later voltages up to 280 can be applied to 
the motors. The running time of the film is reduced to 0.8 of a 
second. There is a timer associated with the camera circuit which 
allows the camera to be set at operating times up to 6 seconds. As- 
sociated with the control unit is an event timer which allows the 
event to be either started or stopped at any predetermined time up to 
6 seconds either ahead of, simultaneously with, or after the camera has 
started. This unit increases the flexibility of the camera tremendously 
and is now currently available. 

The Eastman and Fastax cameras have mounting holes provided in 
their bases for attaching the cameras to standard motion picture tri- 
pods. The cameras are heavy enough to require a reasonably heavy 
tripod and the Mitchell, Bell, Howell, and Akeley tripods as well as 
others of that type are satisfactory. For laboratory usage a drill- 
press stand with a tilt-top table can be used quit satisfactorily. 

Many times it is necessary to reduce the heat of the lamps on the 
subject which is being photographed, therefore, either of two schemes 
can be used. Aklo heat-absorbing glass can be put between the light 
and the subject or a water cell can be used in the same position. The 
Aklo heat-absorbing glass is obtainable either from the Corning Glass 
Works or from the Libbey-0 wens-Ford Glass Company. Water 
cells which are made from glass, rubber seals, and metal housings are 
rather expensive to design and to seal properly. There is a small 
flask available which can be used quite advantageously and that is a 
Pyrex Kolle culture flask. The diameter of this flask is 135 mm and 
the outside distance between the flat walls is 35 mm. This flask is 
portable and can be easily filled just prior to use. 

With the above brief description on how to use the high-speed 
camera the committee has attempted to bring the users up to date on 
the latest developments in the field of high-speed photography in order 
to make it more generally useful. 



High-Speed Motion Pictures by 
Multiple-Aperture Focal-Plane 
Scanners* 

BY FORDYCE E. TUTTLE 

EASTMAN KODAK COMPANY, ROCHESTER, NEW YORK 

Summary Heretofore, in all high-speed photography instantaneous 
time covered one complete frame, the continuity of instantaneous frames 
forming the time axis. This is fundamental even with image dissecting 
methods which reduce frame length by lateral displacement of frame ele- 
ments, a trick done to shorten physically the time axis and allow the higher 
speeds mechanically inherent in less length of film. A new method of ob- 
taining high-speed pictures is described whereby instantaneous time covers 
multiple small portions of a single frame, the total area of these small por- 
tions being sufficient to provide detail and the single frame being large 
enough to permit unmagnified observation. This is accomplished by mul- 
tiple-aperture focal-plane scanners. 

PRACTICALLY EVERY WORKER in the field of high-speed motion 
picture photography has had to make some compromise on picture 
definition to obtain high rates of picture taking. As soon as we 
exceeded the speeds at which we could afford to stop the film mechan- 
ically to receive an image, we all found ourselves in some kind of 
trouble. 

Those who chose to make the image travel with the film by moving 
image reflectors or refractors had to be content with approximations. 
A rather poor image, progressively astigmatized and progressively 
distorted, could be made to move in the same direction as the film. 
Periodically during the picture-taking cycle this image might move 
faster than the film, and periodically it might move slower than the 
film. We had to be satisfied if we could achieve an average image 
velocity that equaled the average film velocity. 

Those who chose stroboscopic illuminating devices attempted to 
make the individual picture exposure time so short that they did not 
care whether the film was moving or not. To obtain more light, they 
could even allow their pictures to blur quite a bit before they pro- 
duced images as bad as the image travel systems. Any self-luminous 
or continuously illuminated objects in their scenes, of course, smeared 
out beyond recognition. 
* Presented April 6, 1949, at the SMPE Convention in New York. 

NOVEMBER, 1949 JOURNAL OF THE SMPE VOLUME 53 451 



452 TUTTLE November 

Those who chose to rely on the image dissection system made no 
attempt to achieve definition in the direction of film travel except by 
the use of multiple-picture elements. There is no pretense of moving 
the image with the film, nor is streaking avoided by chopping the 
light. By restriction of the height of individual elements, it is possible 
to stop the smear every time it becomes too bad. 

All of us have found picture unsteadiness a problem. Imperfect 
picture definition and imperfect picture registration have, therefore, 
always made the collection of motion data for first-, second-, and third- 
derivative analysis difficult. 

The device described here is not in any sense a cure-all for these 
troubles. It is our hope, however, that in some form it might prove 
itself to be useful. 

A chronological history of the development work to date will aid 
this discussion. 

Several years ago Richard Engelken, a well-known consulting 
engineer of New York City, undertook a display-device assignment. 
He conducted several experiments that led him to some interesting 
conclusions. Unfortunately, he died before he completed his studies, 
and only recently have we been able to try out some of his suggestions. 

Very abbreviated and somewhat rephrased, his comments were as 
follows : 

1. With a fine-grain emulsion we are satisfied with definition in a 
picture enlarged as much as thirty diameters (a microfilm standard) . 

2. Let us put that same fine-grain emulsion on a plate thirty diam- 
eters larger than the frame size which we say gives us a satisfactory 
picture. 

3. On this plate, then, without trying to get something for noth- 
ing, we should be entitled to store information sufficient in quantity 
to show thirty times thirty or nine hundred pictures, each with defini- 
tion no better or no worse than that of single smaller pictures. 

4. Now let us not make our nine hundred pictures all condensed 
small images which have to be enlarged for viewing, but let us space 
out the silver grains which are used to display a single picture in some 
orderly extended array so that each picture will be spread over the 
thirty-diameter plate. 

5. This spacing of dots will be exceedingly coarse for the fine-grain 
emulsion used, so coarse in fact that in the neighborhood of each 
picture element there will be room for dots to be used for the eight- 
hundred and ninety-nine other pictures. 



FOCAL-PLANE SCANNERS 453 

To follow these suggestions, we must, of course, provide ourselves 
iih some means for positively selecting those silver grains which we 
to portray a single picture, and make sure that when we take the 




Fig. 1 Composite picture of a landscape, a beach scene, and a young child. 

iage, only those grains are used. When later we wish to show the 
icture, we must not allow the observer to see any image elements 
longing to some other picture. 



454 



TlJTTLE 



November 



A well-made focal plane sieve might do this. Small holes, widely 
spaced in an opaque member placed in contact with the emulsion, 
would allow only the parts of the picture that get through the holes 



> r 



I 




Fig. 2 A landscape. 

to expose the film. If later each hole (or the sieve as a unit) could be 
displaced an amount equal to the diameter of a hole, a second picture 
could be taken on the unexposed parts of the film. In fact, every 



1949 



FOCAL-PLANE SCANNERS 



455 



time we move the holes to a new nonoverlapping position, we can 
take a new picture until we have filled the film with images. Neither 
the film nor the sieve can be allowed any dimensional change between 




Fig. 3 A beach scene. 

the time of exposing and the time of viewing the pictures, if a very 
disturbing scrambling is to be avoided. 

It seemed too ambitious at the start to attempt making an ex- 
tremely accurate sieve and an extremely accurate mechanical system 



456 



TUTTLE 



November 



for two-dimensional scanning. It was, however, decided to attempt 
to make a line screen with dimensions selected to permit thirtj r 
images. One-dimensional scanning by this grid filled the thirty- 








'Fig. 4 A young child. 

diameter film with images. Shrinkage difficulties were minimized 
by having both the grid and the film on glass plates. 

Demonstration of the ability of such a grid to separate images is 
simple. Fig. 1 contains the pictures of a landscape, a beach scene, 



1949 FOCAL-PLANE SCANNERS 457 

and a young child. With unaided viewing, it presents a scrambled 
appearance. However, when we place the same plate behind a grid 
that is similar to the one through which it was multiply exposed, we 
can see fairly good representations of the component subjects. These 
are shown in Figs. 2, 3, and 4. 

The dimensions of the grid and plate may be of interest. The over- 
all size is 10 X 12 inches. One-thousandth-inch transparent lines are 
separated by opaque areas so the lines are on 0.030-inch centers. 
Very few people are able to believe from visual judgment that the 
transparent lines are as narrow as they are. 

SINGLE DIMENSION SCANNING 
WITH MULTIPLE SLIT FOCAL 
PLANE SCANNERS AND 
CAPPIN6 SHUTTERS 




'* 1 

EMULSION--- 



COMPLETE SCANNER AND GUTTER ASSEMBLY 
Fig. 5 

The casual observer, when he is close enough to see the line struc- 
ture, is inclined to guess the white lines are wider than the black 
lines. The effect of this physiological phenomenon is to make the 
picture seem quite continuous, although twenty-nine thirtieths of it 
is missing. 

In order for us to make use of the grid device for motion pictures, 
we need only to place the grid in a focal plane position behind a lens. 
If we move the grid continuously in front of a stationary film plate, 
we shall impress on the plate a series of images portraying the motion 
of whatever is occurring in the object plane of the lens. Since for 



458 



TUTTLE 



November 



each one-thousandth-inch movement of the grid we are entitled to 
have a new position picture of the object, it is obvious that we shall 
not have to move the grid very fast to achieve high-speed motion 
pictures. One inch per second will give the equivalent of one thou- 
sand pictures per second. In spite of the fact that our individual 
picture size is 10 X 12 inches, we need to move the grid only 0.030 
inch to take thirty pictures, instead of the thirty feet we would have 
to move the film to take thirty one-foot high pictures in more orthodox 
ways. Because the film plate is stationary, the image steadiness, of 
course, is excellent. 




Fig. 6 16-mm frame showing high-speed numbers. 

A 4- X 5-inch camera was built to try out the high-speed use of the 
moving-grid system. The grid in this camera was spring driven and 
moved a total of 0.090 inch. During the first one third of this 
motion, no exposure is produced because of the action of a multiple- 
aperture capping shutter. Exposure occurs for the next 0.030 inch, 
and the last third of the motion is used to decelerate the mechanism 
with the slits capped. Fig. 5 shows the performance of the grid and 
capping-shutter system. Picture speeds of 16,000 per second have 
been achieved with the particular spring drive used. 

A motion picture film has been made from the grid playback of 









1949 



FOCAL-PLANE SCANNERS 



459 



pictures taken with this camera. Unfortunately, we have not had 
opportunity to photograph any very romantic subjects, and the 
pictures illustrated are those of white numbers painted on a black belt 
moving across the object field. Fig. 6 shows a reproduction of one 
frame from the 16-mm motion pictures we have taken of the viewing 
grid being motor driven across the exposed developed plate. The 
numbers are quite identifiable even in cases where the images are 
moving as fast as 250 miles per hour on the plate. 




In Fig. 7 we have stopped the translation of the grid in a mid-point 
of image travel. The number aspect you see is the result of a small 
amount of rotation of the grid analyzer. This rotation allows you to 
see an early time picture of the tops of the numbers and a late time 
picture of the bottoms of the numbers. The numbers slant from left 
to right, As the analyzing grid becomes parallel to the taking grid 
position, the numbers straighten up as in Fig. 6 because the top of 
the numbers was taken at the same time as the bottom of the numbers. 
Finally, as the rotation of the grid is reversed, the numbers lean from 
right to left as in Fig. 8 because you are seeing the late time picture 
of the tops of the numbers and an early time picture of the bottoms 
of the numbers. In Fig. 9 the capping shutter was removed from the 



460 



TUTTLE 



November 



camera so that parts of three sequences of pictures are seen. Although 
the belt of numbers was moving at a fixed speed, the multiple images 
appear to be traveling at different speeds. This effect is the result of 
acceleration and deceleration in the grid movement. 

Some very interesting and useful stereoscopic observations can be 
made from a plate contact exposed behind a grid and viewed through 
an analyzing grid, which is held out of contact with the image plate. 
Let us have in the scene five different belts with numbers painted on 
them. One belt is stationary. Two are moving rather fast, one at 




Fig. 8 



a constant velocity and the other at the same average velocity but 
being accelerated. The two others are moving very fast, one again 
at a constant velocity and the other at the same average velocity but 
being decelerated. 

If we view this scene through the separated grid in its parallel 
alignment position, the stationary belt will appear to be in the plane 
of the screen. The two rather fast moving belts will appear coplanar 
but displaced from the screen plane. The two very fast moving belts 
will be in a different plane further displaced from the screen plane. 

If now we rotate the viewing grid, the stationary numbers will 
still appear erect and in the screen plane. The numbers on the belts 



1949 



FOCAL-PLANE SCANNERS 



461 



moving at constant rates will lean over in their own planes, very much 
like the numbers shown in Figs. 7 and 8. The numbers on the 
fastest moving belt will, of course, lean more than those on the slower 
moving belt. The numbers on the belts that are being accelerated 
and decelerated do very interesting things. Rotating the grid 
in one direction will make the numbers lean, of course, but the planes 
of the numbers also tilt, the accelerated numbers tilting their tops 
toward the screen plane and the decelerated numbers tilting their 
bottoms toward the screen plane. 




Fig. 9 Multiple images recorded without the capping shutter. 

Without painstaking measurement of the position of fuzzy unsteady 
pictures, good indications are thus given as to the sign and magnitude 
of the function photographed and its first and second time derivatives. 

Further study should be given to the acuity of stereo interpretation 
of data, and a great deal of work should be put on the use of multiple- 
sequence photography of the type shown in Fig. 9. It is hoped 
to describe in a later paper these subjects as well as a camera 
with a two-dimensional scanning system capable of taking at least 
a thousand pictures at a rate of at least a million pictures per second. 



Improvements in High-Speed 
Motion Pictures by Multiple- 
Aperture Focal- Plane Scanners 

BY FORDYCE E. TUTTLE 

EASTMAN KODAK COMPANY, ROCHESTER, NEW YORK 



Summary It is shown how, with the multiple-aperture scanning 
method of high-speed photography, the absolute number of entirely new 
position pictures of a moving object is more a function of how many grains 
of emulsion are uncovered in the total aperture travel than a function of the 
number of aperture widths uncovered. This results in many more frames 
per event than had been assumed heretofore. A second camera of this 
type is described hi which two-dimensional scanning gives composite pictures 
with a dot structure. This is accomplished by means of a rotating disk. 
This camera is capable of taking high-speed pictures at the rate of at least 
1,000,000 per second. 



AT THE APRIL, 1949, meeting of the Society of Motion Picture 
Engineers in New York a new method of obtaining high-speed 
pictures was described! whereby instantaneous time covers multiple 
small portions of a single large frame, the total area of these small por- 
tions being sufficient to provide detail and the single frame being 
large enough to permit unmagnified observation. This is accom- 
plished by multiple-aperture focal-plane scanners. It is now proposed 
to discuss further certain details of this new approach for the investi- 
gation of high-speed phenomena and to describe a camera of considera- 
bly more flexibility than that shown in April. 

ABSOLUTE NUMBER OF TIME POSITIONS 

Our first attempt to investigate the high-speed aspects of multiple 
apertures moving in a focal plane was described as a spring-driven 
camera with a one-dimensional scanning grid. The dimensions of 
the grid were given as one-thousandth-inch transparent lines separated 
by opaque areas so that the lines are on 0.030-inch centers. Continu- 
ous translation of this grid served to uncover new emulsion as time 

* Presented October 12, 1949, at the SMPE Convention in Hollywood, 
t This issue, pp. 451-461. 

462 NOVEMBER, 1949 JOURNAL OF THE SMPE VOLUME 53 



IMPROVEMENTS IN HIGH-SPEED PICTURES 463 

passed to record composite position pictures of a moving subject. 
Since the process is continuous, the question of how many position 
pictures are recorded in this manner before double exposure takes 
place becomes an important one, and one for which the answer is 
not immediately obvious. As a starting point, one might say that 
for every one-thousandth-inch movement of the grid, an entirely new 
picture could be recorded. On that basis and the grid dimensions 
given we could profess to be able to record thirty composite-position 
pictures on one plate before double exposure results. If that were 
the case, during playback for observation it would be necessary to 
index the analyzing grid one thousandth of an inch to observe a new 
position picture of a moving object, a total indexing of thirty thou- 
sandths of an inch thus passing the thirty position pictures across the 
screen for observation. Even with this assumption one can visualize 
the large number of pictures per second possible by this method, a 
linear grid velocity of only approximately one-half mile per hour giv- 
ing ten-thousand position pictures per second. 

That the above assumption fortunately is pessimistic, and that a 
great many more position pictures of the moving object are actually 
present after 0.030 inch of grid translation, can readily be demon- 
strated. With some thought it becomes apparent that the absolute 
number of pictures of, say, the leading edge of a moving object is more 
a function of how many grains of emulsion are uncovered per 0.030 
inch of travel than a function of the number of slit widths uncovered. 
The total number of "frames" for a grid-type camera would be de- 
termined by the accuracy of one's analysis of the exposed plate. Con- 
crete basis for this claim is the fact that when an exposed high-speed 
composite-picture plate is examined with an analyzing grid, subject 
motion can be observed when the grid is moved less than the trans- 
parent line width or less than one thousandth of an inch. These 
minute subject advances can be seen readily in the table viewer. 
However, they can be better shown to a larger audience by a 16-mm 
demonstration film. 

The first section of this film shows the smoothness of subject mo- 
tion when a plate carrying composite motion picture frames is ex- 
amined through a continuously moving grid. The motion pictures 
were taken continuously of the picture area as the grid scans the 
photographic plate. About two hundred 16-mm frames were exposed 
during the 0.030-inch excursion. The film demonstrated that the 
subject motion is extremely smooth and the picture detail is nearly 



464 TUTTLE November 

equal to that of conventional 16-mm motion pictures even though 
twenty-nine thirtieths of every picture is missing. 

The second part of the film shows that actually at least one hun- 
dred subject positions can be counted. This second part of the film 
was prepared as follows: We arranged to index mechanically an 
analyzing grid in small-step increments across a composite-picture 
plate. We could detect visually subject motion with each minute 
advance. As previously stated, it was found that the grid advance 
for which motion was apparent could be much less than one trans- 
parent slit width. We recorded multiple frames on conventional 16- 
mm film for each of one hundred 0.0003-inch grid advances. In the 
film, the subject appeared to jump from one separate position image 
to another. The subject motion in this case was slow motion but the 
same theory would apply regardless of the subject velocity. (A 
16-mm film demonstration was then made to show the effects 
outlined.) 

The previous statement, that the real number of position pictures 
which exist on a composite plate is a function of emulsion resolution, 
can now be accepted readily. The actual number of jumps which 
one could record as shown on the film may only be limited by one's 
ability to index the scanning grid mechanically in extremely small 
steps. From the foregoing we now see that the performance of our 
previously described, single-dimension scanning camera was con- 
siderably better than claimed. It had been stated from the prelimi- 
nary slit-width subject-position assumption that we had taken motion 
pictures at the rate of 16,000 per second. Since we have now demon- 
strated that one hundred or more position pictures are available for a 
grid movement of 0.030 inch, the 16,000 per second previously claimed 
was actually at least 48,000 frames per second. This more accurate 
picture rate of 48,000 frames per second adds considerable supporting 
evidence for a statement in our previous paper, namely, that we had 
stopped subject motion with the camera when its image speed on the 
film was 250 miles per hour. In a reverse sense, that statement also 
lends considerable weight to our argument here that we must have 
had a good many more than 16,000 frames per second recorded. 
Such image velocities would most assuredly have produced blurred 
images if pictures were taken at the 16,000 rate in the normal sense. 
It is impressive that 48,000 pictures per second can be taken with 
power supplied by only a small simple coiled spring, and it is a relief 
not to have to work under the handicaps of high-speed problems. 



1949 IMPROVEMENTS IN HIGH-SPEED PICTURES 465 

TWO-DIMENSIONAL SCANNING CAMERA 

In our first paper on this subject,! the basic theory proposed a com- 
posite picture made up of widely displaced silver deposits with unex- 
posed areas between them much larger than the deposit size. The 
spacing of the coherent elements for one picture would be so coarse as 
to provide room in the neighborhood of each for elements to be used 
for 899 other pictures. Such a system would require a well-made 
focal-plane sieve for positively selecting those elements which con- 
stitute related parts of a single picture both for exposure and for view- 
ing. Once again if each hole (the sieve as a unit) could be translated 
to a new nonoverlapping position, unexposed emulsion would be un- 
covered for the recording of an entirely new picture. This theory 
requires two-dimensional scanning, a picture now being made up of 
dot elements rather than linear strips as before. A two-dimensional 
scanning system could be made by using two of the one-dimensional 
form described in our first paper and operating at right angles to one 
another. This, however, would be much too complex especially in 
view of the high speeds we wish to attain. A much simpler approach 
is to use a disk carrying a configuration of holes, the disk rotating in a 
camera focal plane to record the composite subject motion frames as 
the event progresses. Such a disk begins to approach the theoretical 
sieve which we proposed in our initial paper. 

A two-dimensional version of the high-speed multiple-aperture 
scanning camera will now be described which is capable of taking 900 
pictures at a rate up to several million per second. These figures are 
based upon the assumption that the number of frames is a function of 
aperture diameters uncovered. This we have now shown to be on the 
low side factorily. However, since we have not done any absolute 
frame-number work for this device similar to that already described 
for the one-dimensional case, this basis will suffice for our preliminary 
introductions. Basically this camera consists of a focal-plane sieve 
in the form of a disk which rotates very nearly in contact with the 
emulsion of a photographic plate on which the images are recorded. 
The camera contains a capping shutter which operates in much the 
same fashion as that described for the one-dimensional case. Fig. 1 
shows the configuration of holes on the disk and the action of the cap- 
ping shutter. On any given radius there is a series of holes one unit 
of length in diameter, each thirty units of length apart. On another 
radius sufficient distance away such that its outermost hole can be 
t This issue, pp. 451^61. 



466 TUTTLE November 

thirty units of length along the periphery from the outermost on the 
previous one, there is an identical radial series of holes. However, on 
this radius each hole along the radius is one unit closer to the center 
than its contemporary on the radius just ahead of it. This process or 
spiraling-in of holes is continued for additional equispaced radii until 
the radius is reached on which the outermost hole is at a distance one 
unit of length from the center greater than the second hole on the 
initial radius considered. Since the separation between the outer- 
most hole and the next one in on any radius is thirty units, this requires 
thirty radii, each with its series one unit closer to the center than its 




TWO DIMENSIONAL 
SCANNING WITH 
MULTIPLE FOCAL PLANE 
APERTURES AND 
CAPPING SHUTTER 

Fig. 1 

predecessor. Since each radial series is separated from its neighbor 
by thirty units on the periphery, the linear distance involved is 900 
units. At this point the configuration is repeated and continued un- 
til the complete disk is covered. Any hole of unit diameter travels 
600 units before it uncovers emulsion which has already been exposed. 
In other words, based upon the frame slit-width function, 900 sepa- 
rate frames are available. At the moment we are using a disk in 
which the hole diameters are one-half thousandth of an inch and the 
separations involved are therefore fifteen thousandths. Such a con- 
figuration, when used to scan a 4 X 5 plate, produces a pattern for 
each frame 240 dots high and 300 wide. The manner of producing 
such a sieve will be the subject of a future paper. 






1949 



IMPROVEMENTS IN HIGH-SPEED PICTURES 



467 



A disk 21 inches in diameter carrying this configuration of holes 
need only be rotated at 500 revolutions per minute to attain a picture- 
taking rate of one million per second. This is the basic picture-taking 
speed of the camera. However, change gears are provided to achieve 
both slower and faster rates of picture taking. A capping shutter 
disk is rotated in assembly with the one already described. This disk 
is identical in all respects to the first except that the holes are now 
slots two and one-half thousandths long and one-half thousandth 
wide. The two disks rotate in assembly until the shutter disk is 
given an added rotational kick by a coil spring. This indexing of the 




DIAGRAMMATIC POSSIBLE 
ARRANGEMENT OF DRIVE 

FOR N16H SPEED 
SCANNER AND SHUTTER 



Fig. 2 

! disks with respect to one another is triggered by the event to be 
photographed. The interaction during indexing between the two is 
shown at the top of Fig. 1 where the arrows represent velocity vec- 

| tors. Exposure takes place as the holes and slots pass through regis- 

| tering position, the length of the slot and its velocity relative to the 
hole being correct to expose all of the emulsion available to a given 

| hole during its translation. The camera construction is such that it 

; may also be used as a viewer for examination of the composite photo- 

| graphic plate. 

Fig. 2 shows the mechanical arrangement for the new high-speed 

| camera. At the top of the figure is shown how a particular scanning 



468 TUTTLE 

hole can proceed for the allowed 900 units of length before arriving at 
emulsion area previously exposed. The exposing and capping shutter 
disks are driven in fixed coupled relation by spur gears from an ordi- 
nary motor. About the shaft and rigidly attached to it is a torsion 
spring which is always trying to index the capping shutter disk coun- 
terclockwise with respect to the hole disk by means of a pin working 
through a slot in the outer shaft and attached to an inner one which 




Fig. 3 Two-dimensional scanning high-speed camera. 

carries the shutter disk. Relative movement between the two disks 
is prevented by a pin attached to the shutter disk and which rests 
against a solenoid arm mounted on the exposing disk. Retraction of 
this arm by an electrical impuse allows the pin to drop into the notch 
thus permitting a small relative movement between the two and caus- 
ing the exposure. Other than the lens used and a means for holding 
the photographic plate, this is all there is to the complete camera. 
Fig. 3 is a rendering of the exterior appearance of the camera. 

We plan to present the results obtained with this camera as the 
context of a further paper on this subject. 






Twenty-Lens High-Speed Camera 

BY CHARLES W. WYCKOFF 

EDGERTON, GERMESHAUSEN, AND GRIER, BOSTON 15, 
MASSACHUSETTS 



Summary A brief description of the Jenkins camera is presented with 
illustrations of the optical principles. In co-operation with the Taylor 
Model Basin, the optical system was redesigned in an attempt to overcome 
faults encountered with the Jenkins camera. Lenses were mounted on 
the rim of the lens wheel instead of the flange. This eliminated one fault 
but introduced others. These faults were all minimized to the extent that 
the resolving power of the camera is better than that of the film. The 20-lens 
camera covers a 35-mm sound aperture and holds up to 200 feet of film. 
It has been operated up to 2350 pictures per second at an //9 effective 
aperture. 



As FAR BACK AS 1910, one of the founders of the Society of Motion 
Picture Engineers, Charles Francis Jenkins, described a non- 
intermittent type of motion picture camera which he had invented. 
It was more than just a motion picture camera, it was in fact, a high- 
speed motion picture camera capable of recording at a rate of approxi- 
mately 3000 pictures per second. This astounding speed was truly 
a great triumph especially since the only film available lacked both 
strength and quality. 

Jenkins achieved these speeds by abolishing the standard practice 
of intermittent motion of the film and using in its stead continuous 
travel. To prevent the image from smearing as the film was moved 
past the picture gate he devised a unique system of image tracking. 
His tracking system consisted of moving a photographic objective 
along with the film; essentially, the camera consisted of several cam- 
eras operating one after the other. As each camera moved into 
position, it recorded an image and then moved away allowing the 
lext camera to commence recording. 

To achieve the seemingly complicated action, Jenkins used a light- 
iight disk or wheel mounted on the shaft of an electric motor, Fig. 
LA. A series of matched focal-length lenses were mounted near the 
rim of the wheel with their optical axes parallel to the wheel axis. 
As the lens wheel was rotated, each lens in turn would sweep past the 

* Presented April 6, 1949, at the SMPE Convention in New York. 

NOVEMBER, 1949 JOURNAL OF THE SMPE VOLUME 53 469 



470 



WYCKOFF 



November 



picture gate. By means of a gear drive from the lens wheel shaft, 
the film was also made to move past the gate in synchronism with the 
motion of the lenses. As each lens was brought into position, it would 
commence recording an image on the film. 

A study of Fig. IB, will show that the image-tracking action 



FILM 




\ ELECTRIC 
MOTOR 



LENS WHEEL 



LENSES 




FILM 



Fig. 1 Schematic of Jenkins camera. 

of the film is not perfect. The film travels along a straight line 
whereas the optical axes of the lenses travel along an arc. Thus the 
image of a point will tend to be a vertical crescent rather than a point. 
This can be clearly seen in Fig. 2, which is a single frame from a high- 
speed motion picture made with this camera. Notice how the small 
self-luminous fragments are all crescent-shaped. This effect can be 



L949 



TWENTY-LENS HIGH-SPEED CAMERA 



471 




Fig. 2 Typical Jenkins camera record. 




Fig. 3 Interior of Jenkins camera. 



472 



WYCKOFF 



November 



minimized by increasing the radius of the lens wheel. It is also neces- 
sary to place a limiting aperture or slit in front of the optical system, 
thereby reducing the distance over which the image is tracked on the 
film. As the radius of the lens wheel increases, the arc becomes more 
nearly a straight line. The radius chosen by Jenkins was on the order 
of 6 inches and the number of lenses was 48. Fig. 3 shows one of 
Jenkins' latest cameras which was constructed about 1914. 




OBJECT 



FILM 




LENS WHEEL 



Fig. 4 Schematic of 20-lens camera. 

The author used the camera a great many times in the early part 
of the war. In co-operation with Taylor Model Basin of the United 
States Navy, an attempt was made to correct the distortion inherent 
in this type of camera. This necessitated a complete redesign of the 
camera and optical system. The first step was to rotate the optical 
axes of the lenses in a plane 90 degrees to the wheel axis used by 



TWENTY-LENS HIGH-SPEED CAMERA 



473 



dns. Instead of being on the flange of the wheel they were 
iced on the rim. Fig. 4 A is a schematic drawing of the optical 
system. The film travels beside the lenses over the same wheel. 
Light passes through the lens which is directly behind the main 
aperture and is reflected by a prism onto the film as shown in Fig. 
4B. A glass prism autocollimator is used instead of mirrors so that a 
2-inch focal-length lens may be used. The physical dimensions are 
too great to allow a 2-inch lens to be used without compensation. The 




ROTATION 
OF IMAGE 







71 


IMAGE - 
MOTION 1 } 


' 


V / 1 MOTION OF 
yr-t | LENS 
1 1 i 



B 
Fig. 5 Limits of image rotation. 

glass of the prism produces this compensation by effectively short- 
ening the optical path of each lens. Focusing is accomplished by 
placing a collimating lens of the correct local length in front of the 
lens wheel. 

At first glance this seems like a simple straightforward answer to 
the problem of eliminating the crescent-shaped distortion prevalent in 
the Jenkins design. Indeed it does eliminate this distortion, but at 
the same time it introduces several other types of distortion into the 
system. First of all, the image and the lens will travel at the same 
speed only if the lens is focused at infinity and with the condition 
that the emergent principal plane of the lens rotates about the same 



474 



WYCKOFF 



November 



radius as the film. Under any other conditions the film will move 
either faster or slower than the image, producing improper tracking 
or distortion smearing. 

A second distortion is caused by the cylindrical section of the film 
plane. It is therefore difficult to have a critically sharp image over 
the entire film. A third distortion called "rotation of image" is 



EMERGENT PRINCIPAL 
PLANE OF LENS 



ROTATI 
LENS I 

( 


ON POINT OF 
9k FILM 


/ 


^ = 




FILM 




- TOTAL IMAGE 
U- DISPLACEMENT 






FILM 
DISPLACEMENT 



DISPLACEMENT 



B 



Fig. 6 Depth-of-focus limits. 



shown in Fig. 5A, the extreme case of such rotation. In this dia- 
gram the lens is rotated about an axis passing through the optical 
axis and the emergent principal plane of the lens. As the lens is 
rotated, so must the film be rotated if the image is to remain sharp. 
If the lens is rotated about a point infinitely distant from the emergent 
principal plane but still on the optical axis there will be no image 
rotation. This is shown in Fig. 5B. To satisfy the conditions of 
image rotation the lens and film should be rotated so that the 



TWENTY-LENS HIGH-SPEED CAMERA 



475 



lergent principal plane of the lens and the film are always par- 
lei. Instead, as seen in Fig. 6A, the lens and film approach one 
tother because both are moving on an arc with the same radius, 
larger radius will minimize this condition until with an infinite 
lius the displacement becomes zero. In Fig. 6B, the prism is 



FLINT GLASS 




R, H-36.0MM 
R 2 = -I9.0MM 
R 3 =-I38.0MM 

D, = 3.5MM 
D= I.5MM 



BACK FOCUS.53.233MM 
FRONT FOCUS,55.43IMM 
EFFECTIVE FOCUS, 55.921 MM 

N D ,THE INDEX OF REFRACTION 
1 OF CROWN GLASS FOR THE 



42 



LJ 



SODIUM LINE, IS 1.5744 

N D ,THE INDEX OF REFRACTION 

1 OF FLINT GLASS FOR THE 

SODIUM LINE, IS 1.6208 
V, , DISPERSION OF CROWN GLASS, IS 57.7 
V 2 > DISPERSION OF FLINT GLASS, IS 36.1 



-0.04 -0.02 
SPHERICAL ABERRATION 
IN MILLIMETERS 




-6 -4 -2 

CURVATURE OF FIELD IN MM 




0.5 1.0 

DISTORTION IN PERCENT 



Fig. 7 Lens characteristics. 

loved for simplicity and the film is placed behind the objective 
stead of alongside it. In the 20-lens camera the radius and limiting 
tperture are such that this displacement never exceeds three tenths 
of a millimeter. The depth of focus of the objectives is sufficient to 
tolerate this much displacement and still resolve 60 lines per milli- 
meter. 

These distortions just mentioned have not been completely elimi- 
nated in this camera. They have, however, been kept to a low enough 



476 



WYCKOFF 



November 



value so that the resolution of the film becomes the limiting factor 
of the camera. 

The lenses selected for this model camera are not by any means an 
optimum choice. They were chosen because they were a standard 
Navy item, readily available, and had characteristics adequate to test 
the usefulness of this type of optical system. These characteristics, 



10 20 30 40 50 60 70 80 90 
OBJECT DISTANCE-FEET 




10 20 30 40 50 60 70 80 90 
OBJECT DISTANCE - FEET 

B 

Fig. 8 Image motion for different object distances. 

shown in Fig. 7, are all suitable for the camera with the exception 
of the curvature of field. The field angle in this camera is approxi- 
mately 13 degrees and at this angle the curvature of the field is great 
enough to cause a blur in the corners of each picture. 

A serious disadvantage of the 20-lens camera is lack of an adequate 
system for focusing. It was previously stated that for perfect image 
tracking the rotating lenses must be focused at infinity. Fig. 8A 
illustrates the amount of motion an imaged point will produce as the 



TWENTY-LENS HIGH-SPEED CAMERA 



477 



>ject distance increases. As the object distance is increased the 
lount of blur decreases. It is obvious from this figure that if the 
tera is to record a scene with a quality superior to the resolution of 
ic film, the object must be at infinity. The lenses are therefore 
ljusted for infinity. To record an object at distances less than 
ifinity, it is necessary to use collimating lenses. For the pilot- 
model camera, three such collimators were selected. These had focal 
lengths of 5 l /z, 8y 4 , and l$ l /z feet, respectively. Thus, if an object 
is placed at 5V 2 feet from the camera with the first collimating lens, 




Fig. 9 Resolution chart as recorded jDy A 20-lens*camera. 
the object will be essentially at infinity. Fig. 8B illustrates the image 
blur as a function of object distance for each of the three collimating 
lenses. It should be noted that at the object distance corresponding 
to the focal length of each collimating lens the amount of blur is zero. 
The optical resolution of this camera is then limited not by im- 
>roper image tracking but rather by (1) image rotation, (2) curvature 
field, and (3) the use of a slit instead of a circular aperture. Image 
rotation can be kept below the value of film resolution by a large- 
leter lens wheel which also reduces film-plane curvature. A 
rectangular or slit aperture undoubtedly reduces the resolving power 



478 WYCKOFF 

of a lens. However, this is still better than the resolution of high- 
speed film. Fig. 9 is a frame from a motion picture of a National 
Bureau of Standards Resolution Chart. The chart was photographed 
at approximately 25 times the focal length. It will be noticed that 
the resolution recorded is probably the resolution of the film or some- 
where around 45 lines per millimeter. 

The only existing model of the 20-lens high-speed motion picture 
camera is the one which was constructed by the Navy, Fig. 10. It 
holds up to 200 feet of standard 35-mm film and has attained a 




Fig. 10 Interior of 20-lens camera. 

speed of 2350 pictures per second. With a more powerful drive motor 
it might be possible to double this speed. The effective aperture is 
//9 and the exposure time is adjustable between approximately 10 
and 60 per cent of the time interval between pictures. The size of 
the image is that of the standard Academy sound aperture. 

A more detailed description of this camera is presented in Navy 
Department David Taylor Model Basin Report R-345. This report 
entitled, "A Twenty-Lens High Speed Motion Picture Camera," may 
be obtained by writing to the David Taylor Model Basin in Washing- 
ton, D. C. 



Half -Million Stationary Images per 
Second With Refocused 
Revolving Beams* 

BY C. D. MILLER 

BATTELLE MEMORIAL INSTITUTE, COLUMBUS 1, OHIO 



Summary A motion picture camera is described, developed in the labo- 
ratories of the National Advisory Committee for Aeronautics, which has 
made photographs of combustion phenomena in an engine cylinder at 
500,000 frames per second. Illustrations and references are included. 
Sample photographs are reproduced. 



THE TIME INVOLVED in the normal nonknocking combustion proc- 
ess in an engine cylinder varies about inversely as engine speed, 
other things being equal. Even with a speed of only 500 revolutions 
per minute the normal combustion process in a single cycle of engine 
operation is completed in less than 10 ~ 2 second. And with.-knocking 
combustion things happen much faster. 

Recent studies in laboratories of the National Advisory Committee 
for Aeronautics 1 have shown that knocking combustion in an engine 
often involves detonation waves traveling more than a mile a second. 
In an engine of 5-inch bore such a wave would move entirely across 
the cylinder in less than 10 ~ 4 second. As this wave usually traverses 
only part of the chamber, it must be "seen" in an interval of only 
2 X 10~ 5 to 4 X 10~ 5 second, if at all. If we want this wave to occupy 
an interval of, say, one second on the projection screen, at 16 frames 
per second, we must photograph at 4 X 10 5 to 8 X 10 6 frames per 
second. 

In response to the demonstrated need in the study of knock, two 
different types of high-speed camera have been developed. The first 2 
has been operated over a period of years at 40,000 frames per second 
in the NACA laboratories, and a slightly modified form of that 
camera now under construction at Battelle Memorial Institute is ex- 
pected to operate at rates up to 100,000 frames per second. 

* Presented April 6, 1949, at the SMPE Convention in New York. 

NOVEMBER, 1949 JOURNAL OF THE SMPE VOLUME 53 479 



480 



MILLER 



November 



The second type of camera, (Fig. 1) which will be discussed here, 
was invented in 1939 and has been described in a United States 
Patent filed 3 December 28, 1940, and in an NAG A note. 4 First photo- 
graphs of combustion were taken with this camera at 10 5 frames per 
second in 1942. The detonation wave involved in engine knock was 
photographed at 2 X 10 5 frames per second in 1944. This series of 
photographs was published 5 in 1946 and again 1 in 1947. Another 
motion picture of engine knock taken with this camera at 5 X 10 5 



Adjusting Screws 
For Mirrors Reflect- 
ing Light Downward 




Fig. 1 Photograph of camera. 



frames per second was exhibited 6 in 1948. It is anticipated that the 
camera will eventually be operated at 10 6 frames per second. 

ELEMENTARY PRINCIPLE OF OPERATION 

The elementary principle of operation is illustrated in Fig. 2 in a 
form designed to expose a series of only two frames. It is remarkable 
that this simple and obvious shutter mechanism apparently remained 
undiscovered 3 until 1939. Besides its use in the camera described 
here, this principle has been used in the Bowen camera, 7 which was, 






1949 HALF-MILLION IMAGES PER SECOND 481 

however, elaborated differently than described in the section of this 
paper on Camera Details. 

In the device as shown in Fig. 2, an objective lens forms a stationary 
primary image on a rotating mirror. The revolving reflected beam 
from the rotating mirror sweeps across the stationary refocusing 
lenses, which are arranged to focus secondary images at two different 
positions on the stationary film. As the primary image is stationary, 
and is located at the center of rotation of the reflected beam, the 
secondary images are also stationary in spite of the rotation of the 
beam. Each secondary image is exposed, however, only during the 



rimary Image 



Rotating Mirror 

Stationary 
Condensing Lens 

Stationary 
Refocusing Lenses 

Stationary 
Secondary 
Images 

-Stationary Film Strip 

Fig. 2 Elementary principle of operation. 

time the reflected beam is sweeping across the refocusing lens cor- 
responding to that image. The arrangement is equivalent to two 
"still" cameras with high-speed shutters timed to open at slightly 
different times. 

The stationary condensing lens shown in Fig. 2 is placed so close to 
the secondary image that it has little effect on the image. Its function 
is to condense the reflected beam into the smallest possible area on the 
surfaces of the refocusing lenses. 

CAMERA DETAILS 

In designing a camera suitable for studies of engine knock, some 
modifications were made on the elementary form shown in Fig. 2. 
The first such change was to eliminate the condensing lens and to 
grind the rotating mirror with a concave curvature, allowing the 



Stationary Ob- 
jective Lens 




482 



MILLER 



Novembei 



mirror to perform the function of condensing the reflected beam. 
This change permitted operation of the mirror through a greater angle 
of rotation than would have been possible with use of the stationary 
condensing lens. 

Figs. 3 and 4 illustrate the camera design used with considerable 



Film 
Strips 



Mirrors 



Refocusing 
Lenses 




Fig. 3 Central horizontal section through camera. 



simplification of mechanical details. Fig. 3 is a central horizontal 
section through the camera and Fig. 4 is a central vertical section. 

Ninety refocusing lenses and four objective lenses are arranged in a 
spherical wall. The refocusing lenses are arranged on six levels, with 
15 lenses on each level. The four objective lenses are on a central 
level, and are seen in section in Fig. 3. The apertures of refocusing 
lenses on three levels may be seen in Fig. 3 below the plane of the 



1949 



HALF-MILLION IMAGES PER SECOND 



section; the other three levels are above that plane and do not appear. 
In Fig. 4, apertures of two of the objective lenses are visible; the 
other two are above the plane of the section. Six of the refocusing 
lenses appear in cross section in Fig. 4, one for each level. Apertures 
of some of the refocusing lenses appear in this view on each of the six 
levels, but nearly half of the refocusing lenses on each level are above 
the plane of the section and are not seen. 

The hexagonal steel rotor, shown alone in Fig. 5, has six highly 
polished concave surfaces, each of which reflects the light beams 
through the refocusing lenses on one of the six levels. 



Master 
Aperture, 



Refocusing Lenses 
Objective Lenses 




Film- ** 
Fig. 4 Central vertical section through camera. 



Fifteen stationary vertical film strips are fitted to the shape of a 
sphere, concentric with and approximately twice as great in radius as 
the spherical wall in which the lenses are mounted. Each 'film strip 
accommodates one refocusing lens on each of the six levels. Each 
film strip is part of a 100-foot roll, 7 / 8 inch wide, arranged by me- 
chanical details, not shown, in such a way that the exposed film can 
be pulled out and cut off after each shot, leaving the camera loaded 
for the next shot. 

Light from the photographic object enters the camera through the 
master aperture seen in Fig. 4 and is reflected by four plane mirrors 



484 MILLER November 

through the four objective lenses. The two objective lenses forming 
the upper (lower) two images as seen on the rotor in Fig. 5 have three 
times the angular spacing between them as have any two adjacent re- 
focusing lenses on a given level. Consequently, secondary images 
formed by light from these two objective lenses are exposed on the 
film strips simultaneously. When the line of intersection of two rotor 
faces cuts across one of the upper (lower) images on the rotor, part of 
this image is refocused on one film strip and part on another. At all 
such tunes, however, the other upper (lower) image is falling full on one 
of the rotor faces and is consequently refocused entirely on one film 
strip. It is therefore possible to secure a continuous, uniformly timed 
series of whole images on the film for a complete turn of the rotor. 

Four objective lenses were provided instead of two in order to 
double the picture-taking frequency and the number of. frames ex- 
posed in a single series. The objective lenses forming the upper 
images in Fig. 5 are offset from those forming 
the lower images by 1 1 /% times the angular spacing 
between two adjacent refocusing lenses. Conse- 
quently, images corresponding to one of these 
pairs of objective lenses are formed on the film 
while the reflected beams corresponding to the 
other pair are falling on the spherical wall between 

two adjacent refocusing lenses. One of the pairs 
Fig. 5 Camera J ..... 

rotor with positions of objective lenses is thus responsible for a uni- 

of four stationary f O rmlv timed series of exposures, 102 in number, 
primary images. / 

during a single turn of the rotor, and these ex- 
posures are interspersed with a similar series exposed by the other 
pair. The two sets can be combined to give 204 successive exposures. 

At many times during a turn of the rotor, two whole images are 
formed on different film strips at the same time. In such cases, the 
better image is used and the other discarded. In general, this pro- 
cedure results in use of more images on the central film strips than the 
outer ones. 

Re-exposure of images on continued turns of the rotor is avoided by 
timing the light flash for the duration of only one turn. Gas-filled 
flash tubes receive the early part of the discharge from a condenser 
whose capacity is sufficient to produce nearly uniform light intensity 
for the period of one rotor turn. At the end of one turn, an elec- 
tronic delay system short-circuits the flash tubes through a grid-con- 
trolled arc tube. 




1949 HALF-MILLION IMAGES PER SECOND 485 

MOTIVE POWER AND ROTOR DYNAMICS 

During early operation of the camera, motive power was supplied 
by an air turbine constructed at the University of Virginia. 8 The 
5-ounce camera rotor was supported by the upper end of the same 
piano-wire shaft, 0.039 inch in diameter, that served the turbine it- 
self. Two babbitt journal bearings were used, one below the turbine 
rotor, the other between the turbine rotor and the camera rotor. The 
upper bearing served to seal the evacuated rotor chamber from the 
atmospheric pressure existing within the air turbine. 

The camera rotor, as seen in Fig. 4, has the appearance of being 
mounted to spin about an axis that makes a considerable angle with 
its own natural axis. At first sight many engineers therefore assume 
that the rotor cannot be balanced properly. The rotor is approxi- 
mately a right prism of hexagonal cross section, with the prism axis 
intersecting the axis of spin at about 15 degrees. It is well known, 
however, that the inertial characteristics of any spinning body may 
be represented by those of an equivalent ellipsoid. It is also well 
known that the fundamental requirement for static and dynamic 
balance is that the body must be mounted to spin about one of the 
principal axes of the equivalent ellipsoid. Moreover, the equivalent 
ellipsoid for any right prism of regular polygonal cross section is a 
spheroid whose major or minor axis coincides with the prism axis. 
By pure coincidence the prismatic camera rotor, designed on the basis 
of optical considerations alone, has almost exactly the correct length 
to make its equivalent spheroid a true sphere. It may, consequently, 
be mounted and balanced to spin about any axis that passes through 
its center of gravity without changing its appearance appreciably. 

The balancing of such a body, however, proved exceedingly difficult. 
The difficulty lay in the facts that the near-spherical body involves 
extremely high critical speeds, that the true axis of balance of the near- 
spherical body may make a large angle with the axis of spin even 
though the unbalance at speeds below 500 revolutions per second is 
barely detectable, and that shaft failure at the critical speed is certain 
if the angle between the true axis of balance and the axis of spin ex- 
ceeds the greatest angular deflection that can be tolerated by the 
shaft. 

After numerous shaft failures at a critical speed of about 1200 
revolutions per second, a better understanding of the problem was 
gradually obtained and it was finally possible to spin the rotor with 



486 MILLER November 

assurance of safety at 5500 revolutions per second, corresponding to 
1.122 X 10 6 frames per second. It was not possible to operate the 
camera at such speed, however, because no solution was found to the 
problem of spattering oil from the journal bearing onto the camera 
lenses. Oil spattering was aggravated by the necessary evacuation of 
the rotor chamber. After some motion pictures of engine knock were 
obtained at 2 X 10 5 frames per second, the air-turbine drive was 
finally abandoned. Work was then started on an electromagnetic 
drive and suspension, modeled after an earlier development at the 
University of Virginia, 9 but with some novel features. The photo- 
graphs recently exhibited, taken at 5 X 10 5 frames per second, were 
obtained with the electromagnetic drive and suspension. 




I 23456 7 

Fig. 6 Selected frames from motion picture of engine knock. 

EXAMPLES OF PHOTOGRAPHS MADE WITH CAMERA 

Fig. 6 presents selected frames from a shot of engine knock obtained 
at 2 X 10 5 frames per second. These photographs have been dis- 
cussed at length elsewhere. 1>5 The first frame of the series was ex- 
posed 25 X 10~ 6 second before knock started to develop, and the 
second frame only 5 X 10 ~ 6 second before the start of knock. Little 
change took place between the exposures of these two pictures because 
the combustion that precedes knock is too slow to produce much 
change in so short a time. 

Approximately the right-hand half of the piston top is seen in each 
frame of Fig. 6, looking downward through a glass window mounted 
in the cylinder head. The spark plug was at the left side of the 
chamber, far outside the field of view. Before the exposures of the 
first two frames the flame traveled all the way across the combustion 
chamber from left to right. In each of these frames, the black cloud 



1949 HALF-MILLION IMAGES PER SECOND 487 

at the right represents the ignited and still-burning gas. The whitish 
mottled region in the left of each frame, on the other hand, represents 
the completely burned gases. 

The third frame of Fig. 6 was taken only 5 X 10~ 6 second later than 
the second frame. The detonation wave known as knock started in 
this third frame, apparently in the burning gases, and caused the 
whitening of the part of the burning zone indicated by the arrows. 

The fourth and fifth frames of the series were taken 5 X 10 ~ 6 and 
15 X 10~ 6 second after the start of knock. Progress of the detonation 
wave in these frames is indicated by the dark-gray (not black) cloud 
in the central part of the picture. The wave traveled both upward and 
downward, as well as toward the left, at nearly 7000 feet per second 
during exposure of these frames. 

The sixth and seventh frames were exposed 35 X 10~ 6 and 60 X 
10 ~ 6 second after the start of knock. In the seventh picture the 
knock reaction has caused a fairly complete disintegration of the 
black combustion zone. In the sixth picture particles of free carbon, 
released by the knock reaction, are seen as small black spots. In the 
seventh frame these particles of free carbon have been smeared out 
into long filaments, because of the effect of their physical inertia as the 
expanding gases rushed by at high speed. 



CONCLUSIONS 

The quality of photographs obtained at rates up to 5 X 10 5 frames 
per second has been such as to provide valuable new information on 
engine knock. Some sacrifice in definition has been made, however, 
: .n order to obtain an extended sequence. It is believed that the 
camera can be redesigned to obtain even a longer sequence, at the same 
speeds, without such sacrifice in definition. 

The camera is inherently limited to use at low relative apertures, 
//ll in this case, but the aperture is adequate for shadow or schlieren 
photography. The aperture is also adequate for direct photography 
of many explosion and detonation phenomena without artificial 
illumination. It is believed that the camera should find wide applica- 
tion in the study of explosion and detonation phenomena, shock 
waves, ballistics, rapid stress changes in mechanical parts as observed 
by photoelasticity, and even the action of very small high-speed 
mechanisms. 



488 MILLER 

REFERENCES 

(1) C. D. Miller, "Roles of detonation waves and autoignition in spark-ignition 
engine knock as shown by photographs taken at 40,000 and 200,000 frames per 
second," SAE Quarterly Trans., vol. 1, pp. 98-143; January, 1947. 

(2) C. D. Miller, "40,000 frames per second," PSA Journal, vol. 14, pp. 669- 
674; November, 1948. 

(3) C. D. Miller, "High-speed motion-picture camera," U. S. Patent Office, 
No. 2400887; May 28, 1946. 

(4) C. D. Miller, "The optical system of the NACA 400,000-frame-per-second 
motion-picture camera," NACA Technical Note No. 1405; August, 1947. 

(5) C. D. Miller, H. L. Olsen, W. O. Logan, Jr., and G. E. Osterstrom, "Analy- 
sis of spark-ignition engine knock as seen in photographs taken at 200,000 frames 
a second," NACA Wartime Report E-239, originally issued as NACA Advance 
Restricted Report No. E6D23; May, 1946. 

(6) T. Male, "Photographs at 500,000 frames per second of combustion and 
detonation in a reciprocating engine," University of Wisconsin, Abstracts of 
Papers, Third Symposium on Combustion and Flame and Explosion Phenomena; 
September 7-11, 1948; published by the University of Wisconsin, Madison, 
Wisconsin. 

(7) "U. S. Navy magnifies time," Product Eng., vol. 19, pp. 147-148; August, 
1948. 

(8) J. W. Beams and F. W. Linke, "An inverted air-driven ultracentrifuge," 
Rev. Sci. Instr., vol. 8 (new ser.), pp. 160-161: May, 1937. 

(9) L. E. MacHattie, "The production of high rotational speed," Rev. Sci. 
Instr., vol. 12, pp. 429-435; September, 1941. 



tery-High-Speed 
rum-Type Camera* 

BY K. M. BAIRD AND D. S. L. DURIE 

NATIONAL RESEARCH LABORATORIES, OTTAWA, ONTARIO, CANADA 



Summary A drum-type camera designed to take pictures at any rate 
up to 200,000 frames per second is described. A total of 1300 frames of the 
16-mm frame size are recorded on a single piece of film from which they can 
be printed directly for projection and analysis. 

THE PRINCIPLES OF THIS CAMERA and the results obtained from an 
improvised model have been described in a paper by Baird 1 in 
1946. Since then an engineered prototype has been built and oper- 
ated up to 125,000 frames per second. 

OPTICAL SYSTEM 

Fig. 1 contains front, side, and top views of a simplified camera 
which illustrate the basic elements of which it is comprised and its 
mode of operation. 

In the top view the lenses LiL 2 . . . L 5 lie in a line behind the edge of 
the rotating disk S whose circumference contains a number of equidis- 
tant slots. Any slot passing in front of the lenses exposes them in the 
order 1, 2,. 3, 4, 5; and with the slots so spaced that when one has 
finished exposing L 5 the next is beginning to expose LI, the lenses are 
exposed repeatedly in the named order. 

In the side view it can be seen that any one of the lenses L forms an 
image of an object in its field at a short distance behind it. This 
image, together with the other four which occur in the same plane, is 
projected by the second lens M via the reflecting face of the revolving 
prism P onto the film wound on the outside of the film drum F. 

The prism P causes the images to travel with a velocity equal to 
that of the film thereby preventing relative motion between the two 
and the consequent blurring of the photographic images. 

The pattern in which the individual pictures fall on the film is 
shown at "D"; each passage of a slot in front of the five lenses pro- 
duces five pictures in a row lying crosswise on the film. From "D" 

* Presented April 6, 1949, at the SMPE Convention in New York. 

NOVEMBER, 1949 JOURNAL OF THE SMPE VOLUME 53 489 



490 



BAIRD AND DURIE 



November 



it can be seen that a row of five frames is laid down in the time re- 
quired to move the film only one frame height. It is evident that for 
a given frame height and a given film velocity, the camera can take 
pictures at five times the rate possible when the film has the width of 
only one frame instead of five. 

A closer inspection of the top view will reveal that the prism P is 
actually cut into five prisms all mounted side by side on one shaft in 
the form of a "stack." In the stack there are as many prisms as 



V TOP 





"B" SIDE 





Fig. 1 Schematic views illustrating the operating principles of the 



there are of the small lenses L and each one of the prisms receives light 
from one of the small lenses. Adjacent prisms are rotated with re- 
spect to one another about the shaft of the prism assembly by an 
angular amount corresponding to the time required for a slot to travel 
between adjacent lenses. 

In effect there are five cameras side by side, each with its own objec- 
tive lens and prism to compensate for film movement ; but all cameras 
place their images on the same piece of film, all use the same projec- 
tion lens, and all are exposed by a common shuttering device. 



1949 



DRUM-TYPE CAMERA 



491 



For the sake of simplicity, the camera just described contained only 
five lenses; the actual camera, whose description follows, contains ten 
lenses. 

Fig. 2 is a perspective view of the basic elements of the camera in 
their correct geometric relationship. Light going in a downward 
direction enters any one of the array of ten small lenses (51) which lie 




Fig. 2 A perspective view of the basic elements 
of the camera in their correct geometric relation- 
ship. 

in a horizontal row below the edge of the slotted disk (24). The 
aerial images they form are projected by the enlarging lenses con- 
tained in the tube (14) via the mirrors (43) and (46) to the surfaces of 
the composite prism (89), from which they are reflected onto the film 
lying (emulsion side inwards) against the inside wall of the film drum 
(86). The slotted disk, the prism assembly, and the film drum are 
synchronized and rotated about their vertical axes by precise gearing. 



492 



BAIRD AND DURIE 



November 



The ten small lenses are ordinary achromats, each with a clear 
aperture of 0.055 inch and a focal length of 0.5 inch. When placed 
side by side the ten occupy a distance of only 1 inch. The slot 
widths, the clear apertures of the lenses, and the lens spacings are 
such that the total exposure time of each lens is equal to the reciprocal 
of the picture rate. 

In the optical tube (14) there is a photographic shutter (59) which 
can be adjusted to stay open during a single revolution of the film 
drum thus preventing the reimposition of images on film area that has 
already been exposed. 




Fig. 3 A cross-sectioned view showing the engineering 
details of the camera. 

The previously mentioned enlarging lenses consist of a Ross "Xpres" 
4-inch wide-angle lens and a Cooke-process anastigmat placed end to 
end. This pair of lenses enlarges the primary images by three times. 

Two grooved rings hold the piece of film against the inside of the film 
drum. The film is 39 inches long by 3 inches wide and holds a total of 
1300 frames. 

Fig. 3 is a sectional view illustrating the mechanical details of the 
machine. The upper chamber contains the slotted disk (24) mounted 
on a shaft which turns on two precision ball bearings. Also mounted 
on the shaft is the gear (30) which meshes with the two gears (31), 



1949 DRUM-TYPE CAMERA 493 

each mounted on the shafts of the identical electric motors (28) and 
(29). In a similar fashion gears attached to the lower ends of the 
motor shafts drive the film drum and the prism assembly; the sec- 
tioned film drum can be clearly seen in the bottom chamber, but the 
prism assembly, somewhat behind the plane of sectioning, is partially 
obscured by the details of the drawing. 

The slotted disk and the film drum are made from forged blanks of 
high-strength Duraluminum. The gears are made from nickel alloy 
and tool steel; their teeth are cut on 15-degree helices and have a normal 
pitch of 32 teeth per inch of diameter. Each elementary prism in the 
10-prism "stack" is of stainless steel and has 20 faces polished to a 
high degree of optical flatness. The electric motors are rated to 
deliver 16 horsepower each at 18,000 revolutions per minute; they 
are of the 3-phase, 2-pole type and are driven by a variable-speed 
alternator. The speed of the machine is measured from the fre- 
quency of the electromotive force induced in the coil (50) by the 
revolving permanent magnet (49) attached to the lower end of the 
film-drum shaft. 

The picture rate for which the camera was designed, namely 200,000 
frames per second, requires that the prism assembly rotate at 60,000 
revolutions per minute, the slotted disk at 30,000 revolutions per 
minute, and the film drum at 9000 revolutions per minute. 

METHOD OF TAKING PICTURES 

Since the picture-taking rate is high enough to expose the whole 
length of the film in Vioo second or less, ordinary magnesium wire 
flashbulbs, whose effective flash duration is of the same order, can be 
used to illuminate the subject. These bulbs are mounted in para- 
bolic reflectors in numbers depending on the picture rate and the 
reflectance of the subject. To take a sequence of pictures the camera 
is accelerated up to the required speed and when that speed is reached 
a timing device trips the camera shutter, the flashbulbs, and the 
event at the proper instants. 

PICTURES TAKEN BY THE CAMERA 

Fig. 4 shows an enlarged portion of a length of film as it comes from 
the camera. It contains a sequence of pictures of a revolving disk 
on which a series of parallel lines and an arrow indicating the direction 
of rotation have been drawn. From the increments of rotation be- 
tween successive frames it can be seen that time is increasing from left 



494 



BAIRD AND DURIE 



November 




1949 DRUM-TYPE CAMERA 495 

to right and from bottom to top. It can be seen also that the pic- 
tures produced by the individual small lenses are of uniform quality. 

From these pictures it is possible to infer approximately the least 
fraction of a frame height that can be resolved: under the best condi- 
tions this is 1 /2so of a frame height. The film used is Kodak Super XX 
Aero. The total field of view of the camera is 11 degrees and the 
aperture of the system is //30. 

Fig. 5 contains pictures of a 0.22-caliber bullet striking a piece of 
plate glass taken at a rate of 100,000 frames per second. Time in- 
creases from left to right. In the first frame the bullet is about to 
touch the glass, in the third it is halfway into the glass, and in the 
fourth, fractures may be seen spreading from the area of impact. 












Fig. 5 A bullet striking a piece of plate glass. The plate glass is shown edge- 
on. A ruler in the background divided in inches gives the scale. The picture 
rate is 100,000 per second. 

CONCLUSIONS 

The speed range in which the camera operates enables it to be used 
in investigations of ballistic and shock-wave phenomena. It takes 
distortion-free pictures with excellent definition of either self-luminous 
or nonluminous events. The use of a 16-mm frame size enables the 
frames to be printed and to be projected with convenience. The 
camera can be moved around the laboratory floor to any required 
position. Further, the ability to record over 1200 frames in a sequence 
in combination with the above features makes the camera a versatile 
laboratory instrument and might uniquely suit it to certain types of 
investigations of shock- wave and ballistic phenomena. 

REFERENCE 

(1) K. M. Baird, "High speed camera," Can. Jour. Res, vol. A24, pp. 41-45; 
July, 1946. 



Design of Rotating Prisms for 
High-Speed Cameras* 

BY JOHN H. WADDELL 

BELL TELEPHONE LABORATORIES, NEW YORK 14, NEW YORK 



Summary Principles of design of rotating prisms for high-speed cameras 
are discussed. A new approach is used in the principles and prisms of 
higher resolution can be obtained by following this unique approach. 



THERE ARE A NUMBER of different types of high-speed motion 
picture cameras being made at present, but the most commonly 
used type is the rotating-prism camera. In this camera the image 
from the lens is projected through a rotating prism, which is so de- 
signed that its rotation causes the image to move in the same direction 
as the film and at the same speed. The rotating-prism-type camera is 
simple in construction and is readily portable, easily used, and adapt- 
able to service under a wide variety of working conditions. 

As the name implies the prism is the novel feature of all rotating- 
prism cameras, and it is the purpose of this paper to discuss the design 
principles of such prisms from the standpoint of good photography. 

Doubtless it has been observed by all that a submerged object 
viewed obliquely appears to be in a position other than is actually the 
case. This is the light passing from one medium to another of 
greater density refracted toward the perpendicular to the interface 
between the two media. When the direction of propagation is from 
the more dense to the less dense medium, the reverse is true. If the 
receiving and emitting interfaces are parallel, the direction of propa- 
gation of light leaving the prism will be parallel to that entering but 
will be offset as indicated in Fig. 1. The amount of offset (ss f in the 
figure) depends upon the magnitude of the refraction effect and the 
thickness of the prism. This is expressed mathematically as 



* Presented October 28, 1948, at the SMPE Convention in Washington. 
496 NOVEMBER, 1949 JOURNAL OF THE SMPE VOLUME 53 



ROTATING-PRISM CAMERA 



497 



Recalling that by definition the index of refraction n is 

sin i 



and that from Fig. 1 



equation (1) can be written 



d = i r 



(2) 
(3) 
(4) 



and the velocity of displacement 

d (ss') fcos i 4 (n 2 sin 2 i) cos 2i sin 2 2i~\ . 

~dt~ T \T 4(n 2 - sin 2 1) -J' 

In (5) k is equal to di/dl, the rotational velocity of the prism which is 
constant. 




Fig. 1 

It follows from (4) that the larger the value of n the smaller the 
value of T will be for a given image displacement. A minimum value 
of T is, of course, desirable for optical reasons and for reducing stresses. 
From (5) it follows that the velocity of the image is more nearly con- 
stant, the larger the value of n and the smaller the value of i. Ex- 
pressed in other words, these deductions mean that the larger the 
value of n and the smaller the angle of rotation of the prism used in 
laying down the image, the less blurring will occur caused by disper- 
sion and to variation between the displacements of the film and the 
image during the period of exposure. Since these are desirable fea- 
tures it follows that maximum values of n and minimum values of T 
and i are desirable design objectives for prisms of rotating prism 
cameras. In a paper published by Kudar, 1 prism design was studied 
from the standpoint of aberrations and it is interesting to note that the 



498 



WADDELL 



November 



design features found to be desirable from that standpoint are iden- 
tical with those above for good design of cameras. 

In order to show how the above design objectives are achieved, it 
will be desirable first to consider the matter of maximum angle of 
incidence i to be used. In this connection, reference is made to Fig. 2, 
a plot of velocities of displacement computed from (5) for various 
values of incidence angle i. It is to be noted that the velocity of the 
image is maximum at angle and decreases rapidly as the angle in- 
creases. By proper choice of gearing for driving the prism the image 

can be kept in step with the 
film within approximately 2 
per cent for angles from to 10 
degrees and hence a maximum 
angle of incidence of 10 degrees 
is a logical value. The angle 
can be limited to this value by 
choice of apertures before and 
in back of the prism. In this 
connection it is of interest to 
note that the cone of light 
from an //2 lens having a 2- 
inch focal length subtends an 
angle of approximately 30 de- 
grees when the object is at 
infinity. If no ray in the 
cone is to strike the prism at 
an angle of incidence of more 
than 10 degrees at any time 
in the rotation of the prism the useful angle subtended by the lens is 
only about 10 degrees. 

Having selected the prism glass for maximum index of refraction 
and having chosen the maximum angle of incidence the next and final 
step in the prism design is to determine its thickness. This involves 
the use of (4). It is first necessary, however, to establish the value 
of ss'. 

It is obvious from .Fig. 1 that ss' is the distance a specific point 
of the image moves during the exposure of the corresponding point 
on the film. It is equally obvious that exposure of the entire scene to 
the film (within one picture frame) does not occur simultaneously but 
proceeds lengthwise on the film as the prism rotates. Having 



















RELATIVE VELOCITY 








TROM EQUATION 5 




^ 


N 








60 






\ 










N 














\ 












\ 














\ 


0* IO* 20* 3O* 40* 5< 


I 


Fig. 2 



1949 ROTATING-PRISM CAMERA 499 

established the maximum angle of incidence (i = 10 degrees in the 
above case), it is evident that the time of exposure of any one point 
on the film is the time required for the prism to rotate through an 
angle of 2i (i.e., 10 degrees to +10 degrees in the above case). In 
a four-sided prism four pictures are exposed per revolution and, 
therefore, the film travels four picture frames per revolution of the 
prism and hence 

4L x 2t 



360 



(6) 



where L is the length of film per picture frame. 

With the value of ss' established and with values of i and n pre- 
viously evaluated, (4) can be solved for the prism thickness to com- 
plete the story of the fundamental design of the prism. Fig. 3 shows 
the calculation for T versus i for varying indexes of refraction for a 
four-sided prism for a 16-mm camera. 

In addition to a suitable prism there are of course a number of other 
technical features that must be incorporated in the camera design if 
satisfactory results are to be obtained. One of these has to do with the 
lengthening of the back focus by the prism. 

Consider a diverging cone of light from the lens toward the film, 

and the prism immersed therein. All rays in the cone not normal to 

the prism face travel a longer path to reach the film plane than do the 

. normal rays. For a ray on the optical axis this increase in back focus 

i. is expressed quantitatively by the equation 



- For rays not on the optical axis the increase is 

F = [~^-i> (8) 



where r is the angle of refraction. In certain cases the back-focus 
effect is sufficient to cause a fuzzy picture at the edges unless corrected 
for by proper design in the lens and in the film sprocket. 

Another point of interest in camera design is the matter of lens 
aperture. As previously indicated only a portion of light from a wide- 
aperture lens is used in a rotating-prism camera. Not only is a large- 
aperture lens therefore uneconomical but it introduces distortion and 
aberrations to reduce the resolving power of the image as shown by 
Kudar. If an exposure can be made at //5.6, an //5,6 lens should be 



500 



WADDELL 



November 



used in preference to an //2.0 lens stopped down to//5.6. Of course, 
increasing the focal length of the lens accomplishes the same effect 
as reducing the aperture. The final objective in this direction is ob- 
tained when using a nearly parallel beam of light through the prism. 
This can be accomplished by a double-lens system where the objec- 
tive lens forms an aerial image ahead of a second lens; the second lens 
focusing this image at the film plane. The second lens should be 




1.4, 

o 

I 



.45 



2 5' 7i 10' I2 15' 

MAX. ANGLE Or INCIDENCE (I) 

Fig. 3 

focused so as to project the aerial image at a 1: 1 magnification. In 
such a system it is comparatively easy to introduce a reticle at the 
plane of the aerial image if such is desired. 

The rotating prism acts as a shutter as well as an image-compensat- 
ing device. In acting as a shutter, as was explained earlier, the time of 
exposure is dependent on the maximum angle of incidence. If the 
prism does not run true, a jumpy picture would be obtained and 
therefore, the housing of the prism shaft must be of sufficient strength j 



L 



ROTATING-PRISM CAMERA 501 



to withstand the centrifugal forces that are present when the prism is 
rotating and the prism must be mounted in such a way and with 
small tolerances that the effects of vibration are eliminated. This 
calls for bearings of extreme precision as well as precision-cut driving 
gears. 

In order to obtain satisfactory results with any rotating-prism 
camera, it is necessary that the prism faces as well as the lens be kept 
clean. 

The data as presented above indicate that high-quality, high-speed 
rotating-prism cameras are possible which will approximate the quality 
obtained with an intermittent-type motion picture camera. The use 
of prism glasses of high index of refraction and low dispersion with 
minimum thickness and minimum angle of incidence, in conjunction 
with suitably designed components such as lenses, sprockets, bear- 
ings, and so forth, produce these results. 

BIBLIOGRAPHY 

(1) J. Kudar, "Optical problems of the image formation in high-speed motion 
picture cameras," J. Soc. Mot. Pict. Eng., vol. 47, pp. 400-403; November, 1946. 

(2) F. E. Tuttle, "A non-intermittent high-speed 16 mm camera," J. Soc. 
Mot. Pict. Eng., vol. 21, pp. 474-478; December, 1933. 

(3) J. L. Boon, "The Eastman high-speed camera Type III," J. Soc. Mot. 
Pict. Eng., vol. 43, pp. 321-327; November, 1944. 

(4) W. Herriott, "High-speed motion picture photography applied to design 
of telephone apparatus," J. Soc. Mot. Pict. Eng., vol. 30, pp. 30-36; January, 
1938. 

(5) Howard J. Smith, "8000 pictures per second, /. Soc. Mot. Pict. Eng., vol. 
45, pp. 171-184; September, 1945. 

(6) John H. Waddell, "Wide angle 35-mm high-speed motion picture camera," 
/. Soc. Mot. Pict. Eng., vol. 46, pp. 87-102; February, 1946. 

(7) J. F. Leventhal, "A new optical compensator," Trans. Soc. Mot. Pict. 
Eng., vol. 12, no. 36, pp. 1068-1075; 1928. 

(8) F. Tuttle and C. D. Reid, "The problem of motion picture projection 
from one continuously moving film," /. Soc. Mot. Pict. Eng., vol. 20, pp. 3-31; 
January, 1933. 

(9) H. D. Taylor, "The image distortion and other effects due to glass thick- 
nesses in lens systems," Proc. Phys. Soc., vol. 46, pp. 283-291; 1934. 

(10) H. D. Taylor, "Image distortion due to glass thickness lens systems, Part 
II," Proc. Phys. Soc., vol. 46, pp. 889-896, 1934. 

(11) H. D. Taylor, "Image distortion on the use of rotating parallel plate glass 
blocks for cinematography and for projection of continuous moving films," Proc. 
Phys. Soc., vol. 49, pp. 663-670; 1937. 

(12) J. Kudar, "Optical problems of the rotating prism cinematograph pro- 
jector," Proc. Phys. Soc., vol. 58, pp. 598-605; 1946. 



Recent British Equipment and 
Technique for High-Speed 
Cinematography* 

BY G. A. JONES AND E. D. EYLES 

RESEARCH LABORATORY, KODAK LTD., HARROW, ENGLAND 

Summary New British cameras for high-speed cinematography are de- 
scribed, among which are included those designed by Marley 1 and by Brails- 
ford and Shrubb. 2 The principles of a new Kerr-cell electro-optical shutter 
which can be used for cinematography are outlined, together with details of 
its performance. New light sources for high-speed cinematography include 
mercury-vapor lamps run at high current densities, and foil-filled flash- 
bulbs fired in rapid succession. Several applications of high-speed cinema- 
tography are described showing how the solutions to engineering problems 
have been obtained when the parts concerned are in rapid motion, especially 
when the amplitudes of the movements are too small to resolve easily in a 
normal record. The vibration characteristics of the anvil of an 8-ton drop- 
forging hammer were determined by the use of a special optical system at- 
tached to the anvil. Because of the widespread disturbance caused by the 
hammer blow, an artificially fixed point in space for reference purposes was 
arranged by means of a long-period damped pendulum system bearing a fi- 
ducial indicator. The surface characteristics of white-hot steel bars were 
studied during high-speed rolling by means of high-speed cinematography 
using ultraviolet light. 

DURING THE PAST two or three years, the use of standard ultrahigh- 
speed cameras for investigational work in Britain has increased, 
and details have. been published of a certain number of highly special- 
ized high-speed cameras. None of these has been aimed at exception- 
ally high picture frequencies, largely because experience has shown 
that even in ballistics work, a frequency of 100,000 frames per second 
is ample, while most ordinary industrial problems can be successfully 
investigated at frequencies of 3000 pictures per second or less. 

In general, these cameras incorporate optical means of compensat- 
ing for the movement of the film, which is in continuous motion, and 
the subject is illuminated continuously. Alternatively, the subject 
is illuminated by a series of flashes of short duration from a gas-dis- 
charge lamp, the flash frequency of which is controlled by a commu- 
tator coupled to the film-driving mechanism of the camera. A fur- 
ther refinement consists in using a combination of synchronized multi- 
ple-flash illumination and optical compensation for film movement. 

* Presented April 6, 1949, at the SMPE Convention in New York. 
502 NOVEMBER, 1949 JOURNAL OF THE SMPE VOLUME 53 



BRITISH HIGH-SPEED CINEMATOGRAPHY 503 

I. CAMERAS 

Senior 3 has described a camera using multiple-flash illumination 
which has been used for studying underwater explosions. This con- 
sists of a flashing light source operated by a commutator coupled to a 
camera capable of transmitting 100 feet of 35-mm film continuously at 
the rate of about 90 feet per second. The highest picture frequency 
obtainable is around 1500 per second, but each individual exposure is 
extremely short, and hence frame-by-frame analysis of the record is 
relatively easy. For photographing small charges, a mirror is used, 
placed at 45 degrees under the surface of the water, but for most work 
the camera and lighting equipment were enclosed in a watertight com- 
partment and completely submerged. The work carried out with 
this camera is particularly interesting, and has included examination 
of the explosion bubble and of the "split" of the water caused by the 
impact of the explosion, the influence of explosions near structures 
including bulkheads of vessels, a photoelastic study of the shock 
waves traveling through solid bodies, and stereophotography, using 
two cameras coupled together. It is claimed that stereo work is par- 
ticularly easy, as the same flash can be used for the two cameras, and 
there is thus no difficulty in maintaining picture synchronism. The 
flash is triggered from one of the cameras, but the film is run through 
both at the same speed. 

Another -interesting camera is that designed by Henry 4 for the study 
of textile fibers during spinning and weaving. This consists of a drum 
camera, illumination being provided by a series of sparks in air or, 
alternatively, flashes from a gas-discharge tube. The equipment is 
capable of taking a series of 120 pictures at a frequency of 1500 per 
second, and can record an object moving at the rate of 10 meters 
(32.81 feet) per second, the accuracy of its position at any instant 
being determinable to within 0.5 mm. Field sizes up to 2 feet in 
diameter have been covered. Henry designed the equipment to be 
made easily in his own workshop at a low cost and succeeded in pro- 
ducing it for under 200 pounds (approximately 800 dollars). It has 
given excellent results, an example of which is shown in Fig. 1, in 
solving problems in the textile field, for which it was designed. 

Brailsford and Shrubb 2 have designed a camera for the photography 
of metallic arc welding, which consists of a drum camera capable of 
taking 25 inches of 35-mm film (Fig. 2). The optical system for com- 
pensating for the film movement consists of a square glass prism ro- 
tated between the back of a conventional folding pocket camera and 



504 JONES AND EYLES November 

the drum carrying the film. One big advantage of the drum camera 
using a short length of film is that it avoids film wastage in photo- 
graphing an operation which takes only a very small time to com- 
plete. Frequencies up to 2500 pictures per second have been at- 
tained, the drum and the glass block being geared together to provide 
correct compensation. A S 1 /?- by 2V2-inch Zeiss camera with a 10.5- 
centimeter //3. 5 lens was used, in conjunction with a drum about 8 
inches in diameter. A special parallel-sided prism of crown glass was 




British Cotton Industry Research Association 

Fig. 1 Single-frame enlargement showing a shuttle emerging from the 
"shed" of a loom. Photographed with P. S. H. Henry's camera at 1500 frames 
per second. 

made and mounted so that four pictures could be taken for each revo- 
lution of the prism. The image is cast on to a narrow slit running 
across the film on the drum at right angles to the direction of its mo- 
tion. By this means, optical correction is improved, because it is 
limited to a small angle of rotation of the prism. With a slit one 
sixteenth of an inch wide, an exposure time as short as 45 micro- 
seconds can be obtained at a frequency of 2500 pictures per second. 
The film drum is made of solid mild steel, the web being lightened by 



1949 



BRITISH HIGH-SPEED CINEMATOGRAPHY 



505 



drilling holes in it. The whole box containing the film drum can be 
detached from the camera for taking to the darkroom. The film is 
held on to the drum by a phosphor-bronze clip, which was found satis- 
factory for speeds of revolution up to 3000 per minute. For the 
photography of arcs, the camera lens was protected by means of a 
sheet of plate glass so that, if it became sputtered, it could be cleaned 
or renewed. 

The camera which problably exhibits the greatest novelty is that 
designed by Marley. 1 It was primarily intended for the study of 
explosive detonations. For this reason, such a camera must be suit- 
able for recording rapid changes in a subject of high luminosity for a 
very short period of time. The picture frequency must be very high, 




Fig. 2 Diagram of Brailsford and Shrubb camera which operates at a rate up 
to 2500 frames per second. 

of the order 100,000 per second; and the exposure time for each pic- 
ture, of the order of a few microseconds. 

The camera (Figs. 3 and 4), consists of a series of 59 lenses, arranged 
round the periphery of a disk about 12 inches in diameter. A second 
fixed disk contains a series of slots, each one-thirty-second of an inch 
wide, forming diaphragms for the lenses, which are 3.5 inches in focal 
length and thus stopped down to an aperture of about //27. An 
annular ring containing a similar series of slots can be moved through 
a small angle to form a shutter to expose all the lenses instantaneously. 
It is actuated by three springs and its opening can be synchronized 
with the detonation by an electromagnetically operated release gear. 

The only continuously moving part of the camera is a disk of 
Hiduminium light alloy containing 16 slots mounted on the shaft of 
an electric motor and rotated continuously at a high speed. 



506 JONES AND EYLES November 

The spring-actuated shutter uncovers the lenses for about 5 milli- 
seconds, during which interval 59 pictures are taken. For a speed of 
rotation of the disk of about 6000 revolutions per minute, a picture 
frequency of approximately 100,000 is obtained, the exposure time 
for each picture being of the order of 5 to 10 microseconds. 

The light transmitted by each lens is reflected, by a small surface- 
aluminized mirror placed at its rear, onto a strip of 35-mm perforated 
film two meters long, held round the inner periphery of a drum. Film 
is drawn from a lighttight cassette and can be returned to it for re- 
moval from the camera for processing. 




Crown Copyright Reserved 

Fig. 3 Marley high-speed camera 
for taking photographs of highly lumi- 
nous subjects, such as explosions, at 
speeds up to 100,000 frames per second. 



A group of eight photographs selected from a series made with 
the Marley camera at the rate of 76,000 frames per second of the 
detonation of a 2-pound charge of the explosive, tetryl, is shown 
in Fig. 5. 

Froome 5 has published details of an interesting Kerr-cell system 
designed for repeat series exposures on a single plate, but adaptable 
for use with a drum camera or any camera using continuously moving 
film. The equipment consists of a standard type of Kerr cell, filled 
with very pure nitrobenzene, across which a potential of about 1000 
volts is maintained. This produces further electrolytic purification 



1949 BRITISH HIGH-SPEED CINEMATOGRAPHY 507 

which, in turn, produces an enhanced Kerr effect. The cell is con- 
trolled by a circuit which can be operated to give any exposure time 
between 0.1 and 6 microseconds at intervals from 4 X 10 ~ 7 to 70 
microseconds. The number of exposures in a sequence can also be 
controlled. For a Kerr cell with plates 1 centimeter long, the electric 
field required for maximum effect is about 33 kilovolts per centimeter. 

LOADING BOX 
/ AUUM*ttS& MIRRORS 



UEAOER- STR?P 9* 
I FILM OUfOES 



MOTOR 8ARNG 

LEVER 



LENSES 




SPEED CONTROL 
RHEOSTAT 

Crown Copyright Reserved 

Fig. 4 Rear view of Marley high-speed camera with back 
plate removed. 

In the case of the equipment built by Froome, plates spaced by 3 mm 
were used, as he employed the equipment behind a microscope eye- 
piece from which the angle of the cone of light was small. To pro- 
duce a larger aperture, a multiple-plate cell connected like a con- 
denser would be needed, but this would have the effect of increasing 
the shortest exposure time possible. For exposures of not less than 1 
microsecond, such a cell could be used behind a lens of 1-centimeter 
diameter, or slightly more. 



508 JONES AND EYLES November 

II. NEW LIGHT SOURCES 

New light sources have been described for use with the conven- 
tional types of mechanical high-speed cameras. The older method 
of using high-efficiency tungsten-filament lamps is being replaced 
steadily by the use of specially modified discharge tubes of various 
types. Beeson 6 has published information on an overrun high-pres- 
sure mercury-cadmium vapor lamp. This lamp can be run at a rela- 
tively low current for prolonged periods, when it gives a light output 
equivalent to about 2 kilowatts of tungsten-filament illumination. 
It can be overrun for short periods, the duration of which depends 
upon the degree of overload, and it then produces an extremely high 
intensity of illumination. For example, when run for one second at 
120 amperes, it provides sufficient light to illuminate a subject 3 feet 
square and give adequate exposure on 16-mm Kodachrome film 
at //2.7, using a Kodak high-speed camera, Type III, running at 
the rate of 3000 pictures per second. The color rendering, though not 
perfect, is sufficiently good for most practical purposes. Beeson 6 has 
also produced special illumination equipment consisting of 48 flash- 
bulbs mounted on a rotating disk and triggered by means of a com- 
mutator so that each bulb is fired in turn as it passes through the re- 
flector. The bulbs are fired at such a rate that substantially uniform 
illumination of the subject is obtained over the one second or so re- 
quired to pass 100 feet of 16-mm film through the Kodak high-speed 
camera running at the rate of 3000 pictures per second. This equip- 
ment has been successfully used with the Kodak high-speed camera in 
several cases where an extremely high intensity of lighting is needed 
without undue heating of the subject. 

Aldington 7 has published information on the gas arc, which con- 
sists of a continuously operated high current-density arc discharge in 
a rare gas, usually xenon. This lamp gives very high illumination for 
extended periods, but it has to be water-cooled. 

III. TIME BASES 

While both conventional high-speed cameras and specially designed 
cameras such as those described above have been used extensively for 
direct photography, there is a growing feeling that straightforward 
cinematography is not adequate for the examination of many prob- 
lems. In the first place, more accurate time bases have had to be in- 
troduced than had previously been used. The inclusion of a specially 



1949 



BRITISH HIGH-SPEED CINEMATOGRAPHY 



509 








510 JONES AND EYLES November 

designed clock or flashing lamp in the picture has not proved satis- 
factory for most types of work carried out at frequencies higher than 
500 pictures per second. For this reason, several specially designed 
time bases have been employed. One of these described by Eyles 8 was 
designed in the Kodak Research Laboratory, at Harrow, England, for 
use with the Kodak high-speed camera, and has been manufactured 
by a firm of instrument makers and fitted to practically all of these 
cameras used in Great Britain. This time base consists essentially 
of an optical system for projecting the image of a condenser, illumi- 
nated by a small tungsten-filament light source, on to the edge of the 
film between the picture and the perforations. The beam of light is 
interrupted by shutter blades on an electrically maintained 500-cycle 
tuning fork. The beam is interrupted twice in each cycle and 1000 
flashes of light per second therefore fall upon the film, to produce 
timing marks in the form of a series of short lines. At high camera 
speeds, these are sufficiently far apart to enable the resulting trace to 
be interpreted easily, but at lower speeds, to prevent overlapping, a 
second shutter is provided for controlling the width of the beam and 
which can be set from outside the time base by means of a dial cali- 
brated in picture frequencies. The whole time base is made up as a 
flat unit which is bolted on to the base of the camera and rests on 
the tripod head. The only modification to the camera, apart from 
fitting the bolts, is the cutting of a hole immediately below the lower 
sprocket through which the optical system can project an image on to 
the film. The unit is energized from the same supply as that used to 
operate the camera. 

Several other experimental time bases have been used, most of 
which depend upon a flashing source of light held close to the film 
inside the camera, the frequency of flash being controlled by a tuning- 
fork system outside. One of the most compact devices consists of a 
tiny plastic case containing a small spark gap and lens which throws 
an image of the spark on to the edge of the film. This is bolted to the 
inside of the camera cover plate, through which two leads run to an 
induction coil and a tuning fork controlling the frequency of sparking. 

IV. UNUSUAL APPLICATIONS OF HIGH-SPEED CAMERAS 

Extensive use of high-speed cinematographic equipment has made it 
clear that there are many thousands of applications for this technique 
in industrial and scientific investigations. Many of the applications 
on record are very similar to those reported in the United States. 



1949 BRITISH HIGH-SPEED CINEMATOGRAPHY 511 

There is, however, one point which does not seem to have been made 
in the literature on high-speed photography so far. It is that the use 
of the technique is frequently limited by the fineness of detail which 
has to be recorded. Engineers requiring to make use of high-speed 
photography often do not realize the fact that although the object to 
be photographed is plainly visible to the camera it does not neces- 
sarily mean that the movement in which they are interested will be 
easily discernible from the photographs produced. The amplitude 
of movement of the subject may be so small that the high-speed 
camera has great difficulty in resolving it. With modern equipment, 
the visual resolving power of the optical system expressed in lines per 
millimeter appears quite high, but the photographic resolving power is 
reduced by low contrast in the final photograph, which is accentuated 
by underexposure, and further degraded by imperfect compensation 
for film movement, and movement of the subject itself during the 
exposure. Thus, relatively small movements may be difficult even 
to detect, let alone accurately measure, unless they can be amplified 
in some way or examined against some fixed point. 

The vibration of a mechanical sieve, which appeared to have quite 
a large amplitude, was extremely difficult to measure from a high- 
speed film record made of part of the sieve itself. The problem 
eventually was solved by embedding a bright steel ball in the surface 
of the sieve and illuminating it with a bright source of light, thus pro- 
ducing a point source of light. By running the high-speed camera at 
a relatively slow rate, this drew out a trace which could be seen on 
the screen and variations in its shape, which were quite marked, gave 
the required information on the changes in the form of vibration of the 
sieve, which could not be detected at all from a film taken of the sieve 
directly, and without resort to this optical trick. 

Another example concerned the examination of the joints in railroad 
lines, and the movement of the fishplates which are used to secure the 
rail ends together. As a locomotive wheel passes over such a joint, 
there is a movement which appears to the eye to have considerable' 
amplitude. Nevertheless, a direct record taken with a high-speed 
camera showed nothing which could be measured accurately. This 
problem was solved simply by placing a dial gauge, calibrated in 
thousandths of an inch, between the underside of the top flange of the 
rail and a large mass of concrete which was laid under the track. The 
readings of this dial gauge could be ascertained easily from a film 
taken of it as the wheel passed over the joint, and the movements of 



512 



JONES AND EYLES 



November 



the rail, thus mechanically amplified, were plotted against time as 
recorded by the camera time base. This method has now been used 
successfully for a large number of applications to industrial problems. 
A more elaborate optical-mechanical arrangement has been de- 
scribed by Eyles 9 and was used in the course of the examination of the 
movement of the anvil of a large drop-forging hammer. The hammer 
itself weighed 8 tons and, after operation for some time, it was found 




005 



005 



O 5 10 

X-OOI SEC. 



Fig. 6 Optical-mechanical arrangement for ex- 
amination of movement of anvil in large drop-forging 
hammer. 

a. Convex lens attached to a reflecting prism 
fastened to anvil to give a uniformly bright disk of 
light that can be photographed. 

b. Method of damping shutter blade with a dash- 
pot so that top edge of blade is just below bottom edge 
of mask on illuminated disk. 

c. Enlarged section of b. 

d. Curve showing amplitude and duration of the 
vibration of the anvil. 

that the foundations of the anvil showed signs of deterioration. The 
noise, flame, and smoke produced when the hammer was dropped were 
such that visual observation of the movement of the anvil was diffi- 
cult, and various observers estimated it at between one hundredth of 
an inch and a quarter of an inch at each blow. Direct photography of 
the anvil was out of the question, owing to the small degree of move- 
ment and the shock transmitted through the surrounding ground. It 
was therefore decided to photograph a point on the anvil in relation 



1949 BRITISH HIGH-SPEED CINEMATOGRAPHY 513 

to a fixed point in space just in front of it. A convex lens attached to a 
reflecting prism was fastened to the anvil, which, by means of suitable 
illumination, presented to the camera lens a uniform disk of light of 
high brightness (Fig. 6a). This was then masked so that only the 
bottom semidisk was visible. A shutter blade was hung in front of 
this, suspended on a long piece of elastic which stretched right across 
the shop, a weight being attached below the point of suspension of 
the shutter. This provided a pendulum of very long period which 
was virtually insensitive to the sudden movement of the anvil, and 
thus provided a fixed point in space with respect to which measure- 
ment of the movement of the anvil could be made. A dashpot below 
the weight assisted in keeping the shutter blade stable by damping its 
movement, and enabled it to be set so that, from the camera view- 
point, its top edge was just below the bottom edge of the mask on the 
illuminated disk (Fig. 6b, 6c). The camera thus saw a narrow hori- 
zontal slit of light which varied in width according to the form of 
vibration of the anvil under the shock of the hammer blow. In this 
way, the amplitude and duration of the vibration of the anvil were 
determined successfully (Fig. 6d). 

In some cases, the use of ultraviolet and infrared illumination has 
been found of value in ultrahigh-speed photography. For example, 
in connection with the photography of the rolling of red-hot steel 
bars, in order to show the surface texture as the bars emerged from 
the rollers, it was found that this could not be observed in high-speed 
films taken in a straightforward manner, because the intrinsic bright- 
ness of the red-hot surface of the bar prevented any rendering of 
texture by external lighting. It was realized, however, that hot metal 
does not emit any appreciable quantity of ultraviolet radiation and 
thus the bars were successfully photographed by means of ultraviolet 
lighting using a Wratten Filter No. ISA over the camera lens to cut 
out all visible light. Ordinary high-speed panchromatic film is suffi- 
ciently sensitive in the region just below the visible to enable a good 
record to be made and, in this region also, the ordinary glass lenses 
are sufficiently transparent to the near ultraviolet. Thus, the use of 
special materials and of quartz lenses was avoided. Infrared illumi- 
nation has also been used for the study of behavior at t{ie electrodes of 
mercury-vapor arcs which normally are difficult to examine, owing to 
the high brightness of the arc itself closely adjacent to the electrode. 
The radiation of infrared light is, however, rather higher from the 
electrode itself than from the arc, thus enabling a satisfactory record 



514 JONES AND EYLES 

to be obtained through the appropriate filter absorbing all visible light 
and transmitting only the near infrared. 

NOTE: Figs. 3, 4, and 5 in this paper are published by permission 
of the Director of Road Research in Great Britain. 

REFERENCES 

(1) W. G. Marley, Unpublished communication. 

(2) F. Brailsford and K. F. Shrubb, "High-speed photography of welding 
arcs/' /. Sci. Instr., vol. 25, pp. 211-213, June, 1948. 

(3) D. A. Senior, "High-speed photographs of underwater explosions," Phot. J. 
vol. 86(B), pp. 25-31; January-February, 1946. 

(4) P. S. H. Henry, "A high-speed cinematograph camera," /. Sci. Instr., vol. 
21, pp. 135-141; August, 1944. 

(5) K. D. Froome, "Electrically operated Kerr cell shutter," J. Sci. Instr. , vol. 
25, pp. 371-373; November, 1948. 

(6) E. J. G. Beeson, "High-intensity light source for high-speed kinematog- 
raphy," Phot. J., vol. 89(B), pp. 62-67; May-June, 1949. 

(7) J. W. Aldington, "The gas arc: A new light source," Engineer (London), 
vol. 186 (4849), p. 675; December 31, 1948. 

(8) E. D. Eyleu, "Simple time-base for a high-speed cine camera," J. Sci. Instr., 
vol. 20, pp. 114-115; 1943. 

(9) E. D. Eyles, "Some applications of high-speed photography," Phot. J., vol. 
83, pp. 261-265; July, 1943. 



Bowen Ribbon-Frame Camera* 

BY E. E. GREEN AND T. J. OBST 

NAVAL ORDNANCE TEST STATION, CHINA LAKE, CALIFORNIA 



Summary A brief background is given of the Bowen ribbon-frame 
camera, as developed for the study of rockets and guided missiles under 
free-flight conditions. The main constructional features are discussed 
as well as the orienting system used on the rocket range. Timing and 
camera-phasing devices are mentioned which make the film record assessable 
to an accuracy of 20 microseconds on the CZR Bowen camera, a model re- 
cently developed to meet the increasingly stringent angular and timing ac- 
curacies needed in the testing of high-velocity missiles. 

INTRODUCTION 

WHEN THE California Institute of Technology was involved in the 
testing of rockets in 1941, it became apparent that a number of 
special cameras would be necessary for metric photography. Ira 
S. Bowen, the present director of the Mount Palomar Observatory, 
was then obtaining and developing photographic equipment for the 
Goldstone rocket range. One of his primary efforts was the construc- 
tion of a camera which would give a record from which rocket posi- 
tions, velocities, and accelerations could be accurately assessed. 

The photographic assessment problem, in determining rocket veloci- 
ties and accelerations, depends on three factors: (1) the accuracy 
with which a rocket position can be determined on film; (2) the ac- 
curacy with which the elapsed time between two frames can be deter- 
mined; and (3) the length of film representing a given displacement 
increment over which the two readings are taken. In plotting results, 
rocket position on each frame plotted versus the time of each frame 
gives a trajectory. The difference between two points on the trajec- 
tory divided by the time increment between the points gives a veloc- 
ity point, and two points on the velocity curve, divided by their 
temporal separation give an acceleration point. Unfortunately, the 
inaccuracies in the trajectory are magnified when the velocity is 
determined and again increased when the acceleration is desired. In 
other words, in taking the first and second derivatives of a trajectory 
obtained by film assessment, the trajectory error causes increasingly 
greater velocity and acceleration errors. 

* Presented October 13, 1949, at the SMPE Convention in Hollywood. 

NOVEMBER, 1949 JOURNAL OF THE SMPE VOLUME 53 515 



516 



GREEN AND OBST 



November 



A camera was needed then, which would have an accurately known 
frame speed, and in addition, since the percentage error in measuring a 
large distance is less than the percentage error in measuring a small 
distance, it was necessary to have the rocket image move as far as 
possible between frames. This necessitated the use of a long focal- 
length lens to produce as much image motion as consistent with de- 









Fig. 1 Bowen ribbon-frame camera being used at present in the study of 
high-velocity rockets and guided missiles. 

sign considerations and also the use of wide film (ribbon frame) to 
give sufficient coverage. The camera which evolved through three 
models-from these considerations is shown in Fig. 1. Since 1944, this 
type of camera has been widely used at the various government rocket 
and missile test centers. . 

As time passed, the inevitable increase in velocities being studied 
made certain improvements necessary in the camera. So, within the 
last year, another step was made in the evolution of the ribbon-frame 
camera. The new camera, called the CZR-1, is shown in Fig. 2. 



! 



1949 BOWEN RIBBON-FRAME CAMERA 517 

This camera was designed by J. A. Clemente and others according to 
specifications written by T. J. Obst and J. A. Clemente of the Meas- 
urements Division at the United States Naval Ordnance Test Station, 
China Lake, California. The Bureau of Aeronautics accepted the 
design and undertook the construction of 32 cameras. The camera 
shown was built by the Aeronautical Photographic Experimental 
Laboratory, Naval Air Materiel Center, Philadelphia, Pennsylvania,* 
and is presently being tested at the Naval Ordnance Test Station. 




Fig. 2 Model CZR-1 Bowen ribuon-frame camera recently developed by 
the Naval Ordnance Test Station and the Aeronautical Photographic 
Experimental Laboratory to meet the increasingly higher requirements 
demanded in the study of rockets and guided missiles. 

CONSTRUCTION OF CAMERA 

All the Bowen ribbon-frame cameras in use have an internal mech- 
anism as diagrammed in Fig. 3, and partially seen in Fig. 2. In the 
following camera discussion, the CZR-1 will be described since it con- 
tains all the essential characteristics of its predecessors plus certain 
improvements . 

The camera parts in Fig. 3 are camera box, B; lens, L; shutter, S; 
housing inside shutter drum, H; film drum, D; framer, F; and maga- 
zine, M . The film comes off the upper spool, PI, inside the magazine, 
loops around the film drum, and is rewound on the lower spool P*. 
The "without-film" speeds of the feed and take-up spools are respec- 
tively lower and higher than the rate at which the film drum rotates, 

* The lens mount, shown in Fig. 2, was designed by the Aeronautical Photo- 
graphic Experimental Laboratory. The lens mount designed by J. A. Clemente is 
under construction. 



518 



GREEN AND OBST 



November 



and slip-clutches in the feed and take-up spools allow for speed variance 
so that the film is kept taut over the film drum. The film used is East- 
man Aerographic Super XX, 5.5 inches wide, loaded in 100-foot rolls. 
Since there are no sprocket holes, the entire width of the film is avail- 
able for pictures and the timing record which will be mentioned later. 
The shutter, which rotates around the housing containing the 
magazine and film-drive mechanism, is a heavy cylinder 14 inches in 
diameter, in which are cut six slots Vs inch wide and 4 3 / 8 inches 
long. The shutter is rotated at 1800 revolutions per minute by a 
synchronous 3-phase, 220-volt, V2-horsepower motor that is bolted to 
the camera box in the position marked SM seen past the operator's 
right arm in Fig. 4. The shutter, built as a heavy unit for dynamic 





Fig. 3 Schematic drawing of Bowen ribbon-frame 
camera. 

stability, is supported entirely by the motor bearings, the shutter and 
motor armature forming an integral element eliminating all in-between 
gears and mechanical linkage. 

At 1800 revolutions per minute, the shutter makes one revolution 
in 1 /ao second, thus the six slots in the shutter drum produce 180 
frames per second. The slots are as evenly spaced around the drum 
as possible. In a test made at Naval Ordnance Test Station, it 
was found that the interframe time interval was l / m second 2.0 
microseconds variation due to mislocation of shutter slots in the drum. 
Indeed, the Boulder-Dam power frequency supplied to the camera 
was in greater error. In assessing the film record, it was found that 
the line frequency was 60.06 cycles per second rather than 60.00. 
These results were obtained, incidentally, by taking Bowen pictures 
of a 1000-cycle-per-second linear oscilloscope sweep controlled by a 



1949 BOWEN RIBBON-FRAME CAMERA 519 

Hewlett-Packard secondary timing standard. The shutter-timing 
record was assessable to an accuracy of about 0.5 microsecond. 

As mentioned above, the six shutter slots make possible a speed of 
180 frames per second. By closing three slots, alternately around 
the drum, pictures can be taken at 90 frames per second. Four slots 
closed, leaving two openings 180 degrees apart, allows 60 frames per 
second; and all closed except one, allows 30 frames per second. In 




Fig. 4 Operator of a Bowen ribbon-frame camera 
orienting the camera in respect to the trajectory by use 
of a gunner's quadrant. The small telescope on top of the 
camera is used for setting one of the needed angles. 

the camera type shown in Fig. 1, the exposure time is about 97 micro- 
seconds and the slot is either fully open or fully closed. In the CZR-1, 
however, various slides can be used in each shutter slot so as to give a 
shutter range from 100 microseconds to the 25 microseconds deemed 
necessary for future work. 

The film moves continuously at 30 inches per second so that at a 
frame speed of 30 frames per second, 3 % of an inch or 1.0 inch of film 
is available for each frame. At 60 frames per second, the frame must 
be reduced to 3 %o or 0.50 inch. Ninety frames per second allows 0.33 



520 GREEN AND OBST November 

inch and at 180 frames per second, only 0.17 inch is available for the 
height of each frame. In practice, the 30 or 60 frames per second 
speed is normally used. The 180 frames per second, due to its narrow 
vertical field of view, is used only when the rocket is restrained on a 
track during the early part of trajectories or where such a frame 
speed is mandatory. 

At each frame speed available, a framer of the necessary dimen- 
sions is inserted in the frame slot F, found in the housing H, just 
ahead of the film, Fig. 3. If the 30 framer is inadvertently used at a 
180-frame-per-second exposure rate, sextuple exposure results. 

Just inside the shutter drum is the housing H, Figs. 2 and 3, which 
contains the film-drive mechanism. The film drive is run by the 
motor MO, Fig. 2, which turns the clutch plate CP, by means of the 
clutch C, fastened directly to the motor shaft. The film drum is pre- 
cision-mounted on special bearings so that the film plane is held con- 
stant to within 0.0002 inch, giving a positive film location. 

The film-drive motor MO is a single-phase continuous-running non- 
synchronous motor. When pictures are to be taken, a signal is sent to 
the camera by either radio link or ground cable. The signal actuates a 
solenoidal-clutch mechanism, not shown, which engages the film-drive 
mechanism with the running motor. Thus, the film moves quickly up 
to full speed, the motor momentum having supplied a considerable 
starting torque. The clutch, shown in Fig. 2, is the coupling by 
which the door-mounted film-drive motor is connected to the film- 
drive mechanism. The door mounting of the motor was designed in 
order to elminate as much strain as possible from the film-drive 
mechanism. 

CAMERA MOUNT 

The camera mount for the CZR-1 has been designed, but as yet has 
not been built. The mount described below is shown in Fig. 1, and is 
the present 3-axis mount. The camera can be positioned in azimuth 
and elevation and rotated about the optic axis of the photographic 
system. In this way, the framer can be set parallel to the trajectory 
being studied. With the camera properly oriented, the optic axis is 
perpendicular to the trajectory and a linear relationship exists be- 
tween motion of the missile along the trajectory and the motion of the 
image on film. This, however, is more in the nature of a simplifica- 
tion of the assessment problem rather than an absolute necessity. 

The camera dolly is built with four jacks, one by each wheel, so 



1949 



BOWEN RIBBON-FRAME CAMERA 



521 



that the camera can be given a solid footing on the ground independ- 
ent of the tires. 

The angles needed to make the optic axis perpendicular to the tra- 
jectory are "set in" at the camera by means of a small sighting tele- 
scope mounted on top of the camera and a gunner's quadrant which 
is set parallel to the proposed trajectory. The quadrant is mounted 
on the camera and the bubble balanced at the angle of the expected 
trajectory, as shown in Fig. 4. 

In the CZR-1, it is intended to mount the camera in a system of 
gimbals around the axes of which are fastened precise scales capable 
of being read to =*=15 seconds of arc. The vernier on the telescope 
shown in Fig. 4 can be read to 1 minute of arc. 

AUXILIARY EQUIPMENT ON CAMERAS 

In determining a trajectory, it is necessary to know the time at 
which each picture was exposed in respect to some instant called "zero 
time" presumably that moment at which the missile began its flight. 
In the Bowen ribbon-frame cameras currently used, the timing con- 
sists of small marks impressed upon the edge of the film every Viooo sec- 
ond by a flashing neon bulb, in the manner shown at the edge of Fig. 5. 

The timing light is so arranged that it is opposite the center of the 
frame when the frame is exposed, so the number of thousand-cycle 
marks on the edge of the frame between centers of adjacent pictures is 
the elapsed time between frames. At the present time, the timing 
marks are counted over a group of frames and divided by the group to 
increase interframe accuracy. This gives rise, of course, to certain 
errors. On the CZR-1, a system is being employed which remedies this 
situation, making accurate time difference measurable for adjacent 
frames. It consists of a binary counting system in which the light 
from a series of flashing neon bulbs is projected through the shutter 
itself and thereby impressed upon the film to give the time of exposure 
to an accuracy of 20 microseconds. A great advantage in the system 
is that the pattern of lighted bulbs impressed on each frame gives the 
additive time measured from "zero time" so that each frame has within 
itself an independent temporal record relating that frame in a definite 
manner to all preceding and succeeding pictures, and to zero time. 

An assessment aid on both cameras consists of three reticles pro- 
jected through the shutters and on to the film. These reticles appear 
on each frame as three small crosses, not shown however in Fig. 5. 
The reticle projectors are constructed so as always to project the 



522 



GREEN AND OBST 



November 



reticles in a constant geometrical relationship in respect to the trajec- 
tory line of each frame. The reticles are then used in assessing the 
film as located points from which all rocket measurements are made. 
In the CZR-1 there will also be included another device known as 
the "star projector." This consists of light from a point source being 
directed by a lens system to three small mirrors and reflected through 
the camera lens and shutter to the film. The three mirrors are plane 



-^m^" 




Fig. 5 Section of Bo wen film in which the 1000-cycle timing marks are 
clearly visible on the right-hand edge. The heavy marks represent a 200-cycle 
beat used in assessment of film to facilitate counting. 

surfaces ground at the proper angles at the end of small rectangular 
quartz bars which are later cemented together. The light from the 
point source is thus divided into three beams which are at a constant 
angular relationship. On the film there will then appear three small 
points of light in a line, the two end points being separated by several 
inches. Thus, each frame has impressed upon it a constant angular 
measure. This is of value in considering the change in focal length 
of a lens system due to the large changes in temperature to which 
cameras used at desert stations are subjected. 



1949 BOWEN RIBBON-FRAME CAMERA 523 

One innovation in the CZR-1 which will be of considerable advan- 
tage is the phasing device incorporated into the shutter motor design. 
By turning a worm gear, it is possible to rotate the field of the motor 
through any desired angular degree. Thus, if two or three CZR-1 's 
are being used simultaneously at 30 frames per second (that is, only 
one shutter slot open), it is possible to adjust the open slots on the 
various cameras so that they are all in the same angular location on 
the rotating shutter drum at the same time. By opening a small 
triangular door in the upper right-hand corner of the camera box. 
above the shutter motor, it is possible to observe the rotating shutter 
by light from a stroboscope unit built in to give a measure of simul- 
taneity at all cameras. The shutter-slot position is adjusted at each 
camera so that it lies at a given mark under the radio-synchronized 
stroblights. By the above device all the cameras can be adjusted to 
take pictures within a few microseconds of simultaneity. When 
desired, it will thus be possible to make allowance for the time delay 
between cameras since the radio carrier which transports the timing 
signal takes longer to reach some cameras than others because of their 
various locations on the range in respect to the transmitting antenna. 

GENERAL 

In the study of rocket-launching problems, it is generally necessary 
to have pictures from which acceleration records can be obtained from 
"zero time" up through the end of burning. Usually this distance is 
larger than can be obtained by a single Bowen ribbon-frame camera 
without making the image too small. The practice is, therefore, to 
use one camera opposite the launcher and as many others as are 
needed down range to cover burning time. The cameras are aligned 
so that the trajectory, covered by one camera, overlaps slightly the 
trajectory covered by the next camera down the line. In this way, a 
continuous record is available for study. One prominent reason for 
redesigning the mount to be used with the CZR-1 lies in the fact that 
the plotted trajectories obtained by each camera join or meet with an 
accuracy limited by the angular devices used to set up the camera's 
optic axis perpendicular to the trajectory. There is, of course, the 
operator error. No device is more accurate than its operator, but 
this is true in all research and testing and it is hoped that the CZR-1 
will provide the means whereby a careful operator can obtain results 
at the high degree of accuracy which is becoming more and more 
necessary at development facilities. 

NOTE: All photographs are official photographs of the United 
States Navy. 



Physical Optic Analysis of Image 
Quality in Schlieren Photography 

BY H. JEROME SHAFER 

PRINCETON UNIVERSITY, PRINCETON, NEW JERSEY 



Summary This paper will consider the schlieren system as a problem in 
physical optics. On the basis of such considerations the effect of aperture, 
focal length, light-source size, and knife-edge position on the quality of 
schlieren photographs will be discussed. First, the mathematical analysis of 
the subject will be briefly presented. On the basis of this analysis the 
schlieren system will be considered using a point source. The case of finite- 
source size then will be discussed. A brief discussion of the effect of astigma- 
tism on the focal length of the system also will be presented. 



INTRODUCTION 

IN SCHLIEREN PHOTOGRAPHY one is usually interested in obtaining 
a photograph with maximum contrast between the images of the 
disturbed and undisturbed regions under study, and of sufficient den- 
sity to render the photograph readily usable. A combination of these 
two factors, contrast and density, may be used as a measure of the 
quality of the schlieren photograph and also of the over-all system. 
The exact definition of quality will vary from individual to individual, 
but the above two factors will usually enter. 

This paper is a discussion, from a theoretical point of view, of the 
effect of the several variables in a schlieren system on the two above- 
mentioned quality parameters. For a given disturbance these vari- 
ables are (1) aperture of the system; (2) focal length of the optics of 
the system; (3) dimension of the light source; and (4) knife-edge 
position. 

The conventional analysis 1 of the schlieren system based on geo- 
metrical optics is in many ways incomplete in its consideration of the 

* Presented October 12, 1949, at the SMPE Convention in Hollywood. This work 

was done under the auspices of the Office of Naval Research, Fluid Mechanics 

Branch (Contract N6ori-270, Task Order No. 6) Project Number NR 061-049, and 

Bureau of Ordnance, Applied Physics Laboratory (Contract NOrd-7920, Task No. 

PRN-2-E). 

524 NOVEMBER, 1949 JOURNAL OF THE SMPE VOLUME 53 






SCHLIEREN PHOTOGRAPHY 



525 



above variables. A more complete analysis may be obtained by treat- 
ingj^he schlieren system as a problem in physical optics, more specifi- 
cally, as a case of modified Fraunhofer diffraction. Physical optic 
analysis of the Foucault test for astronomical objectives, which is the 
basis of Toepler's schlieren system, have been given by Zernike, 2 Lin- 
foot, 3 and Gascoigne. 4 The present paper is an extension of previous 
work, 5 - 6 based on these papers. 




Fig. 1 



ANALYSIS 

Consider the general arrangement for analysis of the diffraction due 
to an aperture A- A in one dimension. 

In Fig. 1, a point source S is located at a distance w from the optic 
axis in the W plane. Light from this source passes through an aper- 
ture A- A in the X plane. It is desired to study the light distribution 
G(y) in the Y plane. 

It can be shown 7 that the complex amplitude of the light vector at 
any point y in the Y plane is given by 



G(y) = const fj 



(1) 



where 



(r 



- (R + fl.) 



526 



SHAFER 



November 



k = 27T/X; X is the wavelength of light emitted by the source S. X 
will be assumed 5000 angstrom units. 

H>(#) is a measure of the phase of any ray at y eminating from S 
passing through a point x in the aperture. G(y) is the resultant of all 
rays passing through the aperture arriving at point y. 

If the light through the aperture is parallel, R and R Q are then 
essentially at infinity so that 

<*>(*) = z( - a). (2) 

Experimentally R and RQ are made infinite by placing a lens or 
mirror between W and X so that W is in the focal plane of the lens or 
mirror. Another lens or mirror is placed between X and Y with Y in 
the focal plane of this second lens or mirror as shown in Fig. 2. 




A 




S*-M 








x 


Ji 


~ 





"^ 


^^ 






< f 


A 








*T 


)-* 



- 4- 



7 



w % Y Z 

Fig. 2 Wind-tunnel schlieren system using lenses for collimator and objective. 

If a wind tunnel of aperture A -A and span D is placed with its 
center line in the X plane, light from $ to y through any point x in the 
aperture will have an additional optical path change of 

0(z) = J^ D [ n ( X) 1) .- l]dl (3) 

where n(x, I) is the index of refraction of the gas in the wind tunnel at 
the point (x, I). If the flow is two-dimensional and the boundary 
layer on the wall perpendicular to the light path is neglected 

- *(*) = [n(x) - 1}D (4) 

n(x) is related to the density of the gas p(x) by the Gladstone-Dale 
law; 

n(x) - I = K P (x). (5) 



1949 



SCHLIEREN PHOTOGRAPHY 



527 



With the additional phase change k$(x\ the complex amplitude of 
the light vector at a point y in the F plane is then given by 



G(y) 



const 



(6) 



-A 



For future mathematical simplicity the effect of the wind tunnel can 
be represented by a complex function f(x) whose amplitude gives the 
light-transmission characteristics of the aperture and whose phase is 
k<j>(x). Since no light is transmitted outside the aperture 

|/(a;)| = 0, \x\ >A \f(x}\ = 1, \x\ < A f(x) = |/(z)|e^(*) 

(6) can be rewritten as 

G(y} = const f^ f (xW**(x)dx. (7) 



u 



s,. 



X Y 2 

Fig. 3 Schematic diagram of the image formation in a schlieren system. 

It can be shown 8 that (7) can be transformed into 

f(x) = const f_^ G(y}e-ik*(x)dy (8) 

where f(x) and G(y) are known as Fourier transforms of each other. 

Equations (7) and (8) indicate that if the object f(x) is known the 
diffraction pattern G(y) can be calculated, and conversely, if the dif- 
fraction pattern G(y) is known, the object f(x) that gave rise to it can 
be calculated. 

This result may be interpreted to mean that a given object f(x) will 
give rise to a diffraction pattern G(y) which will then illuminate some 



528 



SHAFER 



November 



other plane Z in such a manner that the light distribution h(z) in Z is 
the same as the distribution f(x) in X which gave rise to G(y). There 
is a 1 : 1 correspondence between all points in the X plane and those in 
the Z plane. The relative locations of the X and Z planes are given 
by the lens formula 



In most wind-tunnel applications f(x) involves only phase variations 
to which the eye or photographic plate are insensitive. Hence h(z) in 



1Q. 





Fig. 4 Effect of modifying function gf(y) on the diffraction pattern G(y). 
7/1 denotes the cutoff position of the knife-edge. 

the image plane will also involve only phase variation and no detail 
will be seen in the image. 

In the schlieren system the technique employed to render phase 
variations visible is to modify G(y) in some manner g'(y) so that h(z) 
due to this modified G(y) or g(y) is the image of an artificial /(re) which 
would have given rise to- g(y) ; the amplitude distribution of the arti- 
ficial /(x), having a relationship to the phase distribution of the actual 



The modification of the diffraction pattern is usually obtained by 
blocking off a portion of G(y) with a knife-edge or other obstruction. 



1949 SCHLIEREN PHOTOGRAPHY 529 

In general, the modification function g'(y) is similar to that shown in 
Fig. 4. 

g'(y) = - oo < y < yi 

g'(y) = 1 yi < y< + . (9) 

The modified diffraction pattern is then given by 

g(y} = gW X G(y}. (10) 

From (8) 

h(z] = const yi^ g(y}e~ik*(z-)dy. (11) 

Combining (7), (8), and (10) 

Ate) = const yi^ /(a) cte yi". 0'(y)ett*(*-*>dy. (12) 

From Figs. 1 and 2 

a = y/f ao = >//o 

then (2) becomes 



However, since in most systems / = / , 

3>(z) = j(w- y). (13) 

If (13) and (9) are substituted for $(x) and g'(y) in (12) 

where 



(15) 

on integrating (14) 

(16) 



Equation (15) indicates that the effect of varying the light source 
and knife-edge position are complementary and that either or both 
operations produce the same result as adding an optical wedge of 
angle (w + yi) //to the disturbance /(#). 

To find the effect of a light source of finite size, rather than a point 
source one must integrate a function h(z, w) over the dimensions wto 
+w of the light source. This is best done by solving h(z) for several 



530 



SHAFER 



November 



point sources located at different distances from the optic axis in the 
W plane and graphically integrating the resultant. 

The problem as stated in the introduction is to find I(z, \ f(x) , w, yi, 
/) for a given <j>(x) where |/(z) | gives the size of the aperture, w the size 
of the source, yi the knife-edge position, and / the focal length of the 
optics of the system. 



X 



(17) 



To discuss the effect of the several variables mentioned above, a 
simplified disturbance in the X plane as shown in Fig. 5, typical of 
those for which the schlieren-type observation is useful, will be con- 
sidered. This disturbance has two regions of different phase (1) and 



LIGHT a 




X Y Z 

Fig. 5 Typical disturbance to be discussed throughout paper. 

(2) connected by a linear transition region (3) . If a-a is small this dis- 
turbance may represent a shock wave. If a-a is large it may represent 
an expansion or compression. If a = A, the disturbance may 
represent a boundary layer. In Fig. 5, the flow in a wind tunnel, or the 
path of a projectile, will be in the plane of the figure, perpendicular 
to the optic axis. 

To find the light-intensity distribution in the image plane Z due to 
the disturbance of Fig. 5 in the object plane X, equation (16) must 
be integrated. 



1949 SCHLIEREN PHOTOGRAPHY 531 

From the above figure 

f(x) = 0. | x | > A 

f(x} = e~ik4> -A<x<-a (18) 

f(